ratio of word probabilities predicted from brain for bell and airplane

bell	airplane
top 10 words in brain distribution (in article): signal frequency design sound tower common produce time wine record	top 10 words in brain distribution (in article): city build state vehicle Unite road time design world people
top 10 words in brain distribution (not in article): power light station water animal train line locomotive radio steam	top 10 words in brain distribution (not in article): animal house store street town wheel species home car breed
times more probable under bell 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under airplane (words not in the model)
A bell'" is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually an open-ended hollow drum which resonates upon being struck. The striking implement can be a tongue suspended within the bell, known as a "clapper", a small, free sphere enclosed within the body of the bell, or a separate mallet. Bells are usually made of cast metal, but small bells can also be made from ceramic or glass. Bells can be of all sizes: from tiny dress accessories to church bells weighing many tons. Church and temple bells. In the Western world, its most classical form is a church bell or town bell, which is hung within a tower and sounded by having the entire bell swung by ropes, whereupon an internal hinged clapper strikes the body of the bell (called a free-swinging bell). A set of bells, hung in a circle for change ringing, is known as a ring of bells. In the Eastern world, the traditional forms of bells are temple and palace bells, small ones being rung by a sharp rap with a stick, and very large ones rung by a blow from the outside by a large swinging beam. The striking technique is employed worldwide for some of the largest tower-borne bells, because swinging the bells themselves could damage their towers. In the Roman Catholic Church and among some High Lutherans and Anglicans, small hand-held bells, called Sanctus or sacring bells, are often rung by a server at Mass when the priest holds high up first the host, and then the chalice immediately after he has said the words of consecration over them (the moment known as the Elevation). This serves to indicate to the congregation that the bread and wine have just been transformed into the body and blood of Christ (see transubstantiation), or, in the alternative Reformation teaching, that Christ is now bodily present in the elements, and that what the priest is holding up for them to look at is Christ himself (see consubstantiation). Japanese religious bells. Japanese Shintoist and Buddhist bells are used in religious ceremonies. "Suzu", a homophone meaning both "cool and refreshing," are spherical bells which contain metal pellets that produce sound from the inside. The hemispherical bell is the "Kane" bell, which is struck on the outside. See also Kane (musical instrument). Buddhist bells. Buddhist bells are used in religious ceremonies. Bell construed as a cause for war. On January 15, 1602 ("Keichō 7"), a fire broke out at Hōkō-ji, Buddhist temple complex in Kyoto. The great image of the Buddha and the structure housing the statue, the "Daibutsu-den", were both consumed by the flames. In 1610, Toyotomi Hideyori decided to sponsor rebuilding the Hōkō-ji and he also decided to order a great bell cast in bronze. On August 24, 1614 ("Keichō 19"), the huge new bronze bell was cast successfully. Dedication ceremonies were scheduled, but at the last minute, Tokugawa Ieyasu forbade the ceremonies to take place because he construed inscriptions on the bell to have been a personal affront: This contrived dispute led to the, which was a series of battles between armies of the Tokugawa shogunate and the samurai of the Toyotomi clan. The siege lasted through 1615. It is conventionally divided into two stages: the Winter Campaign and the Summer Campaign. In the end, the total destruction of the Toyotomi eliminated the last major opposition to the shogunate which would come to dominate Japan for the next 250 years. Bellmaking. The process of casting bells is called bellmaking or bellfounding, and in Europe dates to the 4th or 5th century. The traditional metal for these bells is a bronze of about 23% tin. Known as "bell metal", this alloy is also the traditional alloy for the finest Turkish and Chinese cymbals. Other materials sometimes used for large bells include brass and iron. Bells are always cast mouth down. Bells are made to exact formulas, so that given the diameter it is possible to calculate every dimension, and its musical note, or tone. The frequency of a bell's note in Hz varies with the square of its thickness, and inversely with its diameter. Much experimentation has been devoted to determining the exact shape that will give the best tone. The thickness of a church bell at its thickest part, called the 'sound bow' is usually one thirteenth its diameter. If the bell is mounted as cast, it is called a "maiden bell" while "tuned bells" are worked after casting to produce a precise note. Bell towers. Bells are also associated with clocks, indicating the hour by ringing. Indeed, the word "clock" comes from the Latin word "cloca", meaning bell. Clock towers or bell towers can be heard over long distances which was especially important in the time when clocks were too expensive for widespread use. In the case of clock towers and grandfather clocks, a particular sequence of tones may be played to represent the hour. One common pattern is called the "Westminster Quarters," a sixteen-note pattern named after the Palace of Westminster which popularized it as the measure used by "Big Ben". Bells as musical instruments. Some bells are used as musical instruments, such as carillons, (clock) chimes, or ensembles of bell-players, called bell choirs, using hand-held bells of varying tones. A "ring of bells" is a set of 4 to twelve bells or more used in change ringing, a particular method of ringing bells in patterns. A peal in changing ringing may have bells playing for several hours, playing 5,000 or more patterns without a break or repetition.. Ancient Chinese bells. The ancient Chinese bronze chime bells called bianzhong or (鐘) are among the highest achievements of Chinese bronze casting technology. These chime bells were used as polyphonic musical instruments and some of these bells have been dated at between 2000 to 3600 years old. The secret of the design and the method of casting zhong bells, which was known only to the Chinese in antiquity, was lost in later generations. It was not fully rediscovered and understood until 1978, when a complete ceremonial set of 65 "zhong" bells was found in a near-perfect state of preservation during the excavation of the of Marquis Yi, who died ca. 430BCE. Yi was ruler of Zeng, one of the Warring States which at the time of his death was under control of the Chǔ state. This region is now part of the present-day Hubei province. Although tuned bells have been created and used for musical performance in many cultures, zhong are unique among all other types of cast bells in several respects. They have a lens-shaped (rather than circular) section and the bell mouth has a distinctive "cutaway" profile, and this special shape gives zhong bells the remarkable ability to produce, depending on where they are struck. The interval between these notes on each bell is either a major or minor third, equivalent to a distance of four or five notes on a piano.. The bells of Marquis Yi, which are still fully playable after almost 2500 years, cover a range of slightly less than five octaves but thanks to their twin-tone capability, the set can sound a complete 12-tone scale, predating the development of the European 12-tone system by some 2000 years, and can play melodies in diatonic and pentatonic scales These bells usually have inscriptions on them from which scholars used as references for studying ancient Chinese writings (also known as Bronzeware script). Another related ancient Chinese musical instrument is called qing (pinyin qing4) but it was made of stone instead of metal. Konguro'o. Konguro'o is a small bell, which as well as Djalaajyn firstly had the utilitarian purposes and only after artistic ones. Konguro'o sounded by the time of moving to the new places, being fastened to the horse harness it created very specific "smart" sound background. Konguro'o also hanged on the neck of leader goat, which leads the flock of sheep in some definite direction. That is why in folk memory almost magic sound of konguro'o was associated with nomadic mode of life. To make this instrument Kyrgyz foremen used cooper, bronze, iron and brass. They also decorated it with artistic carving and covered with silver. Sizes of the instruments might vary in considerable limits, what depended on its function. Every bell had its own timbre. Chimes. A variant on the bell is the tubular bell. Several of these metal tubes which are struck manually with hammers, form an instrument named "tubular bells" or "chimes". In the case of wind or aeolian chimes, the tubes are blown against one another by the wind. Farm bells. Whereas the church and temple bells called to mass or religious service, bells were used on farms for more secular signaling. The greater farms in Scandinavia usually had a small bell-tower resting on the top of the barn. The bell was used to call the workers from the field at the end of the day's work. In folk tradition, it is recorded that each church and possibly several farms had their specific rhymes connected to the sound of the specific bells. An example is the Pete Seeger song "The Bells of Rhymney".	A fixed-wing aircraft'" is an aircraft capable of heavier-than-air flight whose lift is generated not by wing motion relative to the aircraft, but by forward motion through the air. The term is used to distinguish from rotary-wing aircraft or ornithopters, where the movement of the wing surfaces relative to the aircraft generates lift. In the United States and Canada, the term "'airplane'" is used; the term "'aeroplane'" is more common in the rest of the English-speaking countries, including Great Britain, the rest of the Commonwealth countries (excluding Canada), and the Republic of Ireland. These terms refer to any fixed wing aircraft powered by propellers or jet engines. The word derives from the Greek "αέρας" (aéras-) ("air") and "-plane". The spelling "aeroplane" is the older of the two, dating back to the mid-late 19th century. Some fixed-wing aircraft may be remotely or robot controlled. Overview. Fixed-wing aircraft range from small training and recreational aircraft to wide-body aircraft and military cargo aircraft. The word also embraces aircraft with folding or removable wings that are intended to fold when on the ground. This is usually to ease storage or facilitate transport on, for example, a vehicle trailer or the powered lift connecting the hangar deck of an aircraft carrier to its flight deck. It also embraces aircraft with "variable-sweep wings", such as the General Dynamics F-111, Grumman F-14 Tomcat and the Panavia Tornado, which can vary the sweep angle of their wings during flight. There are also rare examples of aircraft which can vary the angle of incidence of their wings in flight, such the F-8 Crusader, which are also considered to be "fixed-wing". The two necessities for fixed-wing aircraft are air flow over the wings for lifting of the aircraft, and an area for landing. The majority of aircraft, however, also need an airport with the infrastructure to receive maintenance, restocking, refueling and for the loading and unloading of crew, cargo and passengers. Some aircraft are capable of take off and landing on ice, aircraft carriers, snow, or calm water. The aircraft is the second fastest method of transport, after the rocket. Commercial jet aircraft can reach up to 1000 km h. Certified single-engined, piston-driven aircraft are capable of reaching up to 435 km h, while Experimental (modified WW II fighters) piston singles reach over 815 km h at the Reno Air Races. Supersonic aircraft (military, research and a few private aircraft) can reach speeds faster than sound. The speed record for a plane powered by an air-breathing engine is held by the experimental NASA X-43, which reached nearly ten times the speed of sound. The biggest aircraft built is the Antonov An-225, while the fastest still in production is the Mikoyan MiG-31. The biggest supersonic jet ever produced is the Tupolev Tu-160. Structure. The structure of a fixed-wing aircraft consists of the following major parts: Some varieties of aircraft, such as flying wing aircraft, may lack a discernible fuselage structure and horizontal or vertical stabilizers. Controls. A number of controls allow pilots to direct aircraft in the air. The controls found in a typical fixed-wing aircraft are as follows: The controls may allow full or partial automation of flight, such as an autopilot, a wing leveler, or a flight management system. Pilots adjust these controls to select a specific attitude or mode of flight, and then the associated automation maintains that attitude or mode until the pilot disables the automation or changes the settings. In general, the larger and or more complex the aircraft, the greater the amount of automation available to pilots. Control duplication. On an aircraft with a pilot and copilot, or instructor and trainee, the aircraft is made capable of control without the crew changing seats. The most common arrangement is two complete sets of controls, one for each of two pilots sitting side by side, but in some aircraft (military fighter aircraft, some taildraggers and aerobatic aircraft) the dual sets of controls are arranged one in front of the other. A few of the less important controls may not be present in both positions, and one position is usually intended for the pilot in command ("e.g.," the left "captain's seat" in jet airliners). Some small aircraft use controls that can be moved from one position to another, such as a single yoke that can be swung into position in front of either the left-seat pilot or the right-seat pilot (i.e. Beechcraft Bonanza). Aircraft that require more than one pilot usually have controls intended to suit each pilot position, but still with sufficient duplication so that all pilots can fly the aircraft alone in an emergency. For example, in jet airliners, the controls on the left (captain's) side include both the basic controls and those normally manipulated by the pilot in command, such as the tiller, whereas those of the right (first officer's) side include the basic controls again and those normally manipulated by the copilot, such as flap levers. The unduplicated controls that are required for flight are positioned so that they can be reached by either pilot, but they are often designed to be more convenient to the pilot who manipulates them under normal condition. Aircraft instruments. "Instruments" provide information to the pilot. "Flight instruments" provide information about the aircraft's speed, direction, altitude, and orientation. "Powerplant instruments" provide information about the the status of the aircraft's engines and APU. "Systems instruments" provide information about the aircraft's other systems, such as fuel delivery, electrical, and pressurization. "Navigation and communication instruments" include all the aircraft's radios. Instruments may operate mechanically or electrically, requiring 12VDC, 24VDC, or 400 Hz power systems. An aircraft that uses computerized CRT or LCD displays almost exclusively is said to have a "glass cockpit." Propulsion. Fixed-wing aircraft can be sub-divided according to the means of propulsion they use. Unpowered aircraft. Aircraft that primarily intended for unpowered flight include gliders (sometimes called sailplanes), hang gliders and paragliders. These are mainly used for recreation. After launch, the energy for sustained gliding flight is obtained through the skilful exploitation of rising air in the atmosphere. Gliders that are used for the sport of gliding have high aerodynamic efficiency. The highest lift-to-drag ratio is 70:1, though 50:1 is more common. Glider flights of thousands of kilometers at average speeds over 200 km h have been achieved. The glider is most commonly launched by a tow-plane or by a winch. Some gliders, called motor gliders, are equipped with engines (often retractable) and some are capable of self-launching. The most numerous unpowered aircraft are hang gliders and paragliders. These are foot-launched and are generally slower, less massive, and less expensive than sailplanes. Hang gliders most often have flexible wings which are given shape by a frame, though some have rigid wings. This is in contrast to paragliders which have no frames in their wings. Military gliders have been used in war to deliver assault troops, and specialized gliders have been used in atmospheric and aerodynamic research. Experimental aircraft and winged spacecraft have also made unpowered landings. Propeller aircraft. Smaller and older propeller aircraft make use of reciprocating internal combustion engines that turns a propeller to create thrust. They are quieter than jet aircraft, but they fly at lower speeds, and have lower load capacity compared to similar sized jet powered aircraft. However, they are significantly cheaper and much more economical than jets, and are generally the best option for people who need to transport a few passengers and or small amounts of cargo. They are also the aircraft of choice for pilots who wish to own an aircraft. Turboprop aircraft are a halfway point between propeller and jet: they use a turbine engine similar to a jet to turn propellers. These aircraft are popular with commuter and regional airlines, as they tend to be more economical on shorter journeys. Jet aircraft. Jet aircraft make use of turbines for the creation of thrust. These engines are much more powerful than a reciprocating engine. As a consequence, they have greater weight capacity and fly faster than propeller driven aircraft. One drawback, however, is that they are noisy; this makes jet aircraft a source of noise pollution. However, turbofan jet engines are quieter, and they have seen widespread usage partly for that reason. The jet aircraft was developed in Germany in 1931. The first jet was the Heinkel He 178, which was tested at Germany's Marienehe Airfield in 1939. In 1943 the Messerschmitt Me 262, the first jet fighter aircraft, went into service in the German Luftwaffe. In the early 1950s, only a few years after the first jet was produced in large numbers, the De Havilland Comet became the world's first jet airliner. However, the early Comets were beset by structural problems discovered after numerous pressurization and depressurization cycles, leading to extensive redesigns. Most wide-body aircraft can carry hundreds of passengers and several tons of cargo, and are able to travel for distances up to 17,000 km. Aircraft in this category are the Boeing 747, Boeing 767, Boeing 777, the upcoming Boeing 787 and Airbus A380, Airbus A300 A310, Airbus A330, Airbus A340, Airbus A380, Lockheed L-1011 TriStar, McDonnell Douglas DC-10, McDonnell Douglas MD-11, Ilyushin Il-86, and Ilyushin Il-96. Jet aircraft possess high cruising speeds (700 to 900 km h, or 400 to 550 mph) and high speeds for take-off and landing (150 to 250 km h). Due to the speed needed for takeoff and landing, jet aircraft make use of flaps and leading edge devices for the control of lift and speed, as well as thrust reversers to direct the airflow forward, slowing down the aircraft upon landing. Supersonic jet aircraft. Supersonic aircraft, such as military fighters and bombers, Concorde, and others, make use of special turbines (often utilizing afterburners), that generate the huge amounts of power for flight faster than the speed of the sound. Flight at supersonic speed creates more noise than flight at subsonic speeds, due to the phenomenon of sonic booms. This limits supersonic flights to areas of low population density or open ocean. When approaching an area of heavier population density, supersonic aircraft are obliged to fly at subsonic speed. Due to the high costs, limited areas of use and low demand there are no longer any supersonic aircraft in use by any major airline. The last Concorde flight was on 26 November 2003. Unmanned Aircraft. An aircraft is said to be 'unmanned' when there is no person in the cockpit of the plane. The aircraft is controlled only by remote controls or other electronic devices. Rocket-powered aircraft. Experimental rocket powered aircraft were developed by the Germans as early as World War II (see Me 163 Komet), and about 29 were manufactured and deployed. The first fixed wing aircraft to break the sound barrier in level flight was a rocket plane- the Bell X-1. The later North American X-15 was another important rocket plane that broke many speed and altitude records and laid much of the groundwork for later aircraft and spacecraft design. Rocket aircraft are not in common usage today, although rocket-assisted takeoffs are used for some military aircraft. SpaceShipOne is the most famous current rocket aircraft, being the testbed for developing a commercial sub-orbital passenger service; another rocket plane is the XCOR EZ-Rocket; and there is of course the Space Shuttle. Ramjet aircraft. A ramjet is a form of jet engine that contains no major moving parts and can be particularly useful in applications requiring a small and simple engine for high speed use, such as missiles. The D-21 Tagboard was an unmanned Mach 3+ reconnaissance drone that was put into production in 1969 for spying, but due to the development of better spy satellites, it was cancelled in 1971. The SR-71's Pratt & Whitney J58 engines ran 80% as ramjets at high speeds (Mach 3.2). The SR-71 was dropped at the end of the Cold War, then brought back during the 1990s. They were used also in the Gulf War. The last SR-71 flight was in October 2001. Scramjet aircraft. Scramjet aircraft are in the experimental stage. The Boeing X-43 is an experimental scramjet with a world speed record for a jet-powered aircraft Mach 9.7, nearly 12,000 km h (≈ 7,000 mph) at an altitude of about 36,000 meters (≈ 110,000 ft). The X-43A set the flight speed record on 16 November 2004. History. The dream of flight goes back to the days of pre-history. Many stories from antiquity involve flight, such as the Greek legend of Icarus and Daedalus, and the Vimana in ancient Indian epics. Around 400 BC, Archytas, the Ancient Greek philosopher, mathematician, astronomer, statesman, and strategist, was reputed to have designed and built the first artificial, self-propelled flying device, a bird-shaped model propelled by a jet of what was probably steam, said to have actually flown some 200 meters. This machine, which its inventor called "The Pigeon" (Greek: "Περιστέρα" "Peristera"), may have been suspended on a wire or pivot for its flight. Amongst the first recorded attempts at aviation were the attempts made by Yuan Huangtou in the 6th century and by Abbas Ibn Firnas in the 9th century. Leonardo da Vinci researched the wing design of birds and designed a man-powered aircraft in his "Codex on the Flight of Birds" (1502). In the 1630s, Lagari Hasan Çelebi flew in a rocket artificially powered by gunpowder. In the 18th century, Francois Pilatre de Rozier and Francois d'Arlandes flew in an aircraft lighter than air, a balloon. The biggest challenge became to create other craft, capable of controlled flight. Sir George Cayley, the founder of the science of aerodynamics, was building and flying models of fixed-wing aircraft as early as 1803, and he built a successful passenger-carrying glider in 1853. In 1856, Frenchman Jean-Marie Le Bris made the first powered flight, by having his glider "L'Albatros artificiel" pulled by a horse on a beach. On 28 August 1883, the American John J. Montgomery made a controlled flight in a glider. Other aviators who had made similar flights at that time were Otto Lilienthal, Percy Pilcher and Octave Chanute. The first self-powered aircraft was created by an Englishman by the name of John Stringfellow of Chard in Somerset, who created a self-powered model aircraft that had its first successful flight in 1848. Clément Ader constructed and designed a self-powered aircraft. On October 9, 1890, Ader attempted to fly the Éole, which succeeded in taking off and flying uncontrolled a distance of approximately 50 meters before witnesses. In August 1892 the Avion II flew for a distance of 200 meters, and on October 14, 1897, Avion III flew a distance of more than 300 meters. Richard Pearse made a poorly documented uncontrolled flight on March 31, 1903 in Waitohi, New Zealand, and on August 28, 1903 in Hanover, the German Karl Jatho made his first flight. Alberto Santos-Dumont, a Brazilian living in France, built the first practical dirigible balloons at the end of the nineteenth century. In 1906 he flew the first fixed wing aircraft, the "14-bis", which was of his and Gabriel Voisin's design. A later design of his, the "Demoiselle", introduced ailerons and brought all around pilot control during a flight. The Wright Brothers made their first successful test flights on December 17, 1903. This flight is recognized by the Fédération Aéronautique Internationale (FAI), the standard setting and record-keeping body for aeronautics and astronautics, as "the first sustained and controlled heavier-than-air powered flight". By 1905, the Wright Flyer III was capable of fully controllable, stable flight for substantial periods. World War I served as a testbed for the use of the aircraft as a weapon. Initially seen by the generals as a "toy", aircraft demonstrated their potential as mobile observation platforms, then proved themselves to be machines of war capable of causing casualties to the enemy. "Fighter aces" appeared, described as "knights of the air"; the greatest (by number of air victories) was the German Manfred von Richthofen, the "Red Baron". On the side of the allies, the ace with the highest number of downed aircraft was René Fonck, of France. Following the war, aircraft technology continued to develop. Alcock and Brown crossed the Atlantic non-stop for the first time in 1919, a feat first performed solo by Charles Lindbergh in 1927. The first commercial flights took place between the United States and Canada in 1919. The turbine or the jet engine was in development in the 1930s; military jet aircraft began operating in the 1940s. Aircraft played a primary role in the Second World War, having a presence in all the major battles of the war, Pearl Harbor, the battles of the Pacific, the Battle of Britain. They were an essential component of the military strategies of the period, such as the German Blitzkrieg or the American and Japanese aircraft carrier campaigns of the Pacific. In October 1947, Chuck Yeager was the first person to exceed the speed of sound, flying the Bell X-1. Aircraft in a civil military role continued to feed and supply Berlin in 1948, when access to railroads and roads to the city, completely surrounded by Eastern Germany, were blocked, by order of the Soviet Union. The first commercial jet, the de Havilland Comet, was introduced in 1952. A few Boeing 707s, the first widely successful commercial jet, are still in service after nearly 50 years. The Boeing 727 was another widely used passenger aircraft, and the Boeing 747 was the world's biggest commercial aircraft between 1970 and 2005, when it was surpassed by the Airbus A380. Designing and constructing an aircraft. Small aircraft can be designed and constructed by amateurs as homebuilts, such as Chris Neil's Woody Helicopter. Other aviators with less knowledge make their aircraft using pre-manufactured kits, assembling the parts into a complete aircraft. Most aircraft are constructed by companies with the objective of producing them in quantity for customers. The design and planning process, including safety tests, can last up to four years for small turboprops, and up to 12 years for aircraft with the capacity of the A380. During this process, the objectives and design specifications of the aircraft are established. First the construction company uses drawings and equations, simulations, wind tunnel tests and experience to predict the behavior of the aircraft. Computers are used by companies to draw, plan and do initial simulations of the aircraft. Small models and mockups of all or certain parts of the aircraft are then tested in wind tunnels to verify the aerodynamics of the aircraft. When the design has passed through these processes, the company constructs a limited number of these aircraft for testing on the ground. Representatives from an aviation governing agency often make a first flight. The flight tests continue until the aircraft has fulfilled all the requirements. Then, the governing public agency of aviation of the country authorizes the company to begin production of the aircraft. In the United States, this agency is the Federal Aviation Administration (FAA), and in the European Union, Joint Aviation Authorities (JAA). In Canada, the public agency in charge and authorizing the mass production of aircraft is Transport Canada. In the case of the international sales of aircraft, a license from the public agency of aviation or transports of the country where the aircraft is also to be used is necessary. For example, aircraft from Airbus need to be certified by the FAA to be flown in the United States and vice versa, aircraft of Boeing need to be approved by the JAA to be flown in the European Union. Quieter aircraft are becoming more and more needed due to the increase in air traffic, particularly over urban areas, as noise pollution is a major concern. MIT and Cambridge University have been designing delta-wing aircraft that are 25 times more silent (63 dB) than current craft and can be used for military and commercial purposes. The project is called the Silent Aircraft Initiative, but production models will not be available until around 2030. Industrialized production. There are few companies that produce aircraft on a large scale. However, the production of an aircraft for one company is a process that actually involves dozens, or even hundreds, of other companies and plants, that produce the parts that go into the aircraft. For example, one company can be responsible for the production of the landing gear, while another one is responsible for the radar. The production of such parts is not limited to the same city or country; in the case of large aircraft manufacturing companies, such parts can come from all over the world. The parts are sent to the main plant of the aircraft company, where the production line is located. In the case of large aircraft, production lines dedicated to the assembly of certain parts of the aircraft can exist, especially the wings and the fuselage. When complete, an aircraft goes through a set of rigorous inspection, to search for imperfections and defects, and after being approved by the inspectors, the aircraft is tested by a pilot, in a flight test, in order to assure that the controls of the aircraft are working properly. With this final test, the aircraft is ready to receive the "final touchups" (internal configuration, painting, etc), and is then ready for the customer. Comparisons. There are three main statistics which may be used to compare the safety of various forms of travel: It is worth noting that the air industry's insurers base their calculations on the "number of deaths per journey" statistic while the industry itself generally uses the "number of deaths per kilometre" statistic in press releases. Causes. The majority of aircraft accidents are a result of human error on the part of the pilot(s) or controller(s). After human error, mechanical failure is the biggest cause of air accidents, which sometimes also can involve a human component; e.g., negligence of the airline in carrying out proper maintenance. Adverse weather is the third largest cause of accidents. Icing, downbursts, and low visibility are often major contributors to weather related crashes. Birds have been ranked as a major cause for large rotor bursts on commercial turboprop engines, spurring extra safety measures to keep birds away. Technological advances such as ice detectors also help pilots ensure the safety of their aircraft.