The mechanical structure of an aircraft is known as the airframe. This structure is typically considered to include the fuselage, undercarriage, empennage and wings, and excludes the propulsion system. 
Airframe design is a field of aerospace engineering that combines aerodynamics, materials technology and manufacturing methods with a focus on weight, strength and aerodynamic drag, as well as reliability and cost.
Modern airframe history began in the United States when a 1903 wood biplane made by Orville and Wilbur Wright showed the potential of fixed-wing designs.
In 1912 the Deperdussin Monocoque pioneered the light, strong and streamlined monocoque fuselage formed of thin plywood layers over a circular frame, achieving 210 km/h (130 mph).  
Many early developments were spurred by military needs during World War I. Well known aircraft from that era include the Dutch designer Anthony Fokker's combat aircraft for the German Empire's Luftstreitkräfte , and U.S. Curtiss flying boats and the German/Austrian Taube monoplanes. These used hybrid wood and metal structures.
By the 1915/16 timeframe, the German Luft-Fahrzeug-Gesellschaft firm had devised a fully monocoque all-wood structure with only a skeletal internal frame, using strips of plywood laboriously "wrapped" in a diagonal fashion in up to four layers, around concrete male molds in "left" and "right" halves, known as Wickelrumpf (wrapped-body) construction  - this first appeared on the 1916 LFG Roland C.II, and would later be licensed to Pfalz Flugzeugwerke for its D-series biplane fighters.
In 1916 the German Albatros D.III biplane fighters featured semi-monocoque fuselages with load-bearing plywood skin panels glued to longitudinal longerons and bulkheads; it was replaced by the prevalent stressed skin structural configuration as metal replaced wood.  Similar methods to the Albatros firm's concept were used by both Hannoversche Waggonfabrik for their light two-seat CL.II through CL.V designs, and by Siemens-Schuckert for their later Siemens-Schuckert D.III and higher-performance D.IV biplane fighter designs. The Albatros D.III construction was of much less complexity than the patented LFG Wickelrumpf concept for their outer skinning.[ original research? ]
German engineer Hugo Junkers first flew all-metal airframes in 1915 with the all-metal, cantilever-wing, stressed-skin monoplane Junkers J 1 made of steel.  It developed further with lighter weight duralumin, invented by Alfred Wilm in Germany before the war; in the airframe of the Junkers D.I of 1918, whose techniques were adopted almost unchanged after the war by both American engineer William Bushnell Stout and Soviet aerospace engineer Andrei Tupolev, proving to be useful for aircraft up to 60 meters in wingspan by the 1930s.
The J 1 of 1915, and the D.I fighter of 1918, were followed in 1919 by the first all-metal transport aircraft, the Junkers F.13 made of Duralumin as the D.I had been; 300 were built, along with the first four-engine, all-metal passenger aircraft, the sole Zeppelin-Staaken E-4/20.   Commercial aircraft development during the 1920s and 1930s focused on monoplane designs using Radial engines. Some were produced as single copies or in small quantity such as the Spirit of St. Louis flown across the Atlantic by Charles Lindbergh in 1927. William Stout designed the all-metal Ford Trimotors in 1926. 
The Hall XFH naval fighter prototype flown in 1929 was the first aircraft with a riveted metal fuselage : an aluminum skin over steel tubing, Hall also pioneered flush rivets and butt joints between skin panels in the Hall PH flying boat also flying in 1929.  Based on the Italian Savoia-Marchetti S.56, the 1931 Budd BB-1 Pioneer experimental flying boat was constructed of corrosion-resistant stainless steel assembled with newly developed spot welding by U.S. railcar maker Budd Company. 
The original Junkers corrugated duralumin-covered airframe philosophy culminated in the 1932-origin Junkers Ju 52 trimotor airliner, used throughout World War II by the Nazi German Luftwaffe for transport and paratroop needs. Andrei Tupolev's designs in Joseph Stalin's Soviet Union designed a series of all-metal aircraft of steadily increasing size culminating in the largest aircraft of its era, the eight-engined Tupolev ANT-20 in 1934, and Donald Douglas' firms developed the iconic Douglas DC-3 twin-engined airliner in 1936.  They were among the most successful designs to emerge from the era through the use of all-metal airframes.
In 1937, the Lockheed XC-35 was specifically constructed with cabin pressurization to undergo extensive high-altitude flight tests, paving the way for the Boeing 307 Stratoliner, which would be the first aircraft with a pressurized cabin to enter commercial service. 
During World War II, military needs again dominated airframe designs. Among the best known were the US C-47 Skytrain, B-17 Flying Fortress, B-25 Mitchell and P-38 Lightning, and British Vickers Wellington that used a geodesic construction method, and Avro Lancaster, all revamps of original designs from the 1930s. The first jets were produced during the war but not made in large quantity.
Due to wartime scarcity of aluminum, the de Havilland Mosquito fighter-bomber was built from wood—plywood facings bonded to a balsawood core and formed using molds to produce monocoque structures, leading to the development of metal-to-metal bonding used later for the de Havilland Comet and Fokker F27 and F28. 
Postwar commercial airframe design focused on airliners, on turboprop engines, and then on jet engines. The generally higher speeds and tensile stresses of turboprops and jets were major challenges.  Newly developed aluminum alloys with copper, magnesium and zinc were critical to these designs. 
Flown in 1952 and designed to cruise at Mach 2 where skin friction required its heat resistance, the Douglas X-3 Stiletto was the first titanium aircraft but it was underpowered and barely supersonic; the Mach 3.2 Lockheed A-12 and SR-71 were also mainly titanium, as was the cancelled Boeing 2707 Mach 2.7 supersonic transport. 
Because heat-resistant titanium is hard to weld and difficult to work with, welded nickel steel was used for the Mach 2.8 Mikoyan-Gurevich MiG-25 fighter, first flown in 1964; and the Mach 3.1 North American XB-70 Valkyrie used brazed stainless steel honeycomb panels and titanium but was cancelled by the time it flew in 1964. 
A computer-aided design system was developed in 1969 for the McDonnell Douglas F-15 Eagle, which first flew in 1974 alongside the Grumman F-14 Tomcat and both used boron fiber composites in the tails; less expensive carbon fiber reinforced polymer were used for wing skins on the McDonnell Douglas AV-8B Harrier II, F/A-18 Hornet and Northrop Grumman B-2 Spirit. 
Airbus and Boeing are the dominant assemblers of large jet airliners while ATR, Bombardier and Embraer lead the regional airliner market; many manufacturers produce airframe components.[ relevant? ]
The vertical stabilizer of the Airbus A310-300, first flown in 1985, was the first carbon-fiber primary structure used in a commercial aircraft; composites are increasingly used since in Airbus airliners: the horizontal stabilizer of the A320 in 1987 and A330/A340 in 1994, and the center wing-box and aft fuselage of the A380 in 2005. 
The Cirrus SR20, type certificated in 1998, was the first widely produced general aviation aircraft manufactured with all-composite construction, followed by several other light aircraft in the 2000s. 
The Boeing 787, first flown in 2009, was the first commercial aircraft with 50% of its structure weight made of carbon-fiber composites, along with 20% Aluminum and 15% titanium: the material allows for a lower-drag, higher wing aspect ratio and higher cabin pressurization; the competing Airbus A350, flown in 2013, is 53% carbon-fiber by structure weight.  It has a one-piece carbon fiber fuselage, said to replace "1,200 sheets of aluminum and 40,000 rivets." 
The 2013 Bombardier CSeries have a dry-fiber resin transfer infusion wing with a lightweight aluminium-lithium alloy fuselage for damage resistance and repairability, a combination which could be used for future narrow-body aircraft.  In 2016, the Cirrus Vision SF50 became the first certified light jet made entirely from carbon-fiber composites.
In February 2017, Airbus installed a 3D printing machine for titanium aircraft structural parts using electron beam additive manufacturing from Sciaky, Inc. 
Airframe production has become an exacting process. Manufacturers operate under strict quality control and government regulations. Departures from established standards become objects of major concern. 
A landmark in aeronautical design, the world's first jet airliner, the de Havilland Comet, first flew in 1949. Early models suffered from catastrophic airframe metal fatigue, causing a series of widely publicised accidents. The Royal Aircraft Establishment investigation at Farnborough Airport founded the science of aircraft crash reconstruction. After 3000 pressurisation cycles in a specially constructed pressure chamber, airframe failure was found to be due to stress concentration, a consequence of the square shaped windows. The windows had been engineered to be glued and riveted, but had been punch riveted only. Unlike drill riveting, the imperfect nature of the hole created by punch riveting may cause the start of fatigue cracks around the rivet.
The Lockheed L-188 Electra turboprop, first flown in 1957 became a costly lesson in controlling oscillation and planning around metal fatigue. Its 1959 crash of Braniff Flight 542 showed the difficulties that the airframe industry and its airline customers can experience when adopting new technology.
The incident bears comparison with the Airbus A300 crash on takeoff of the American Airlines Flight 587 in 2001, after its vertical stabilizer broke away from the fuselage, called attention to operation, maintenance and design issues involving composite materials that are used in many recent airframes.    The A300 had experienced other structural problems but none of this magnitude.
An aircraft is a vehicle or machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors, and hot air balloons.
Monocoque, also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word monocoque is a French term for "single shell".
The fuselage is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage, which in turn is used as a floating hull. The fuselage also serves to position the control and stabilization surfaces in specific relationships to lifting surfaces, which is required for aircraft stability and maneuverability.
A flying wing is a tailless fixed-wing aircraft that has no definite fuselage, with its crew, payload, fuel, and equipment housed inside the main wing structure. A flying wing may have various small protuberances such as pods, nacelles, blisters, booms, or vertical stabilizers.
A jet airliner or jetliner is an airliner powered by jet engines. Airliners usually have two or four jet engines; three-engined designs were popular in the 1970s but are less common today. Airliners are commonly classified as either the large wide-body aircraft, medium narrow-body aircraft and smaller regional jet.
The Boeing Sonic Cruiser was a concept jet airliner with a delta wing–canard configuration. It was distinguished from conventional airliners by its delta wing and high-subsonic cruising speed of up to Mach 0.98. Boeing first proposed it in 2001, but airlines generally preferred lower operating costs over higher speed. Boeing ended the Sonic Cruiser project in December 2002 and shifted to the slower, but more fuel-efficient 7E7 airliner.
Glare is a fiber metal laminate (FML) composed of several very thin layers of metal interspersed with layers of S-2 glass-fiber pre-preg, bonded together with a matrix such as epoxy. The uni-directional pre-preg layers may be aligned in different directions to suit predicted stress conditions.
An airplane or aeroplane is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spectrum of uses for airplanes includes recreation, transportation of goods and people, military, and research. Worldwide, commercial aviation transports more than four billion passengers annually on airliners and transports more than 200 billion tonne-kilometers of cargo annually, which is less than 1% of the world's cargo movement. Most airplanes are flown by a pilot on board the aircraft, but some are designed to be remotely or computer-controlled such as drones.
Cabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for passengers and crew flying at high altitudes. For aircraft, this air is usually bled off from the gas turbine engines at the compressor stage, and for spacecraft, it is carried in high-pressure, often cryogenic, tanks. The air is cooled, humidified, and mixed with recirculated air if necessary before it is distributed to the cabin by one or more environmental control systems. The cabin pressure is regulated by the outflow valve.
The Rockwell X-30 was an advanced technology demonstrator project for the National Aero-Space Plane (NASP), part of a United States project to create a single-stage-to-orbit (SSTO) spacecraft and passenger spaceliner. Started in 1986, it was cancelled in the early 1990s before a prototype was completed, although much development work in advanced materials and aerospace design was completed. While a goal of a future NASP was a passenger liner capable of two-hour flights from Washington to Tokyo, the X-30 was planned for a crew of two and oriented towards testing.
A blended wing body (BWB), also known as blended body or hybrid wing body (HWB), is a fixed-wing aircraft having no clear dividing line between the wings and the main body of the craft. The aircraft has distinct wing and body structures, which are smoothly blended together with no clear dividing line. This contrasts with a flying wing, which has no distinct fuselage, and a lifting body, which has no distinct wings. A BWB design may or may not be tailless.
A twinjet or twin-engine jet is a jet aircraft powered by two engines. A twinjet is able to fly well enough to land with a single working engine, making it safer than a single-engine aircraft in the event of failure of an engine. Fuel efficiency of a twinjet is better than that of aircraft with more engines. These considerations have led to the widespread use of aircraft of all types with twin engines, including airliners, fixed-wing military aircraft, and others.
In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction also sharing the loads where it is used. There may be more than one spar in a wing or none at all. Where a single spar carries most of the force, it is known as the main spar.
An aerostructure is a component of an aircraft's airframe. This may include all or part of the fuselage, wings, or flight control surfaces. Companies that specialize in constructing these components are referred to as "aerostructures manufacturers", though many larger aerospace firms with a more diversified product portfolio also build aerostructures.
The Junkers J 1, nicknamed the Blechesel, was an experimental monoplane aircraft developed by Junkers & Co. It was the world's first all-metal aircraft.
The Bristol M.R.1 was an experimental biplane with an aluminium monocoque fuselage and metal wings, produced by Bristol during the First World War. Two were built to government order.
Carbon fiber-reinforced polymers, carbon-fibre-reinforced polymers, carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic, also known as carbon fiber, carbon composite, or just carbon, are extremely strong and light fiber-reinforced plastics that contain carbon fibers. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and stiffness (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, sports equipment, and an increasing number of consumer and technical applications.
The aircraft design process is a loosely defined method used to balance many competing and demanding requirements to produce an aircraft that is strong, lightweight, economical and can carry an adequate payload while being sufficiently reliable to safely fly for the design life of the aircraft. Similar to, but more exacting than, the usual engineering design process, the technique is highly iterative, involving high level configuration tradeoffs, a mixture of analysis and testing and the detailed examination of the adequacy of every part of the structure. For some types of aircraft, the design process is regulated by civil airworthiness authorities.
The fuel economy in aircraft is the measure of the transport energy efficiency of aircraft. Efficiency is increased with better aerodynamics and by reducing weight, and with improved engine BSFC and propulsive efficiency or TSFC. Endurance and range can be maximized with the optimum airspeed, and economy is better at optimum altitudes, usually higher. An airline efficiency depends on its fleet fuel burn, seating density, air cargo and passenger load factor, while operational procedures like maintenance and routing can save fuel.
The period between 1945 and 1979 is sometimes called the post-war era or the period of the post-war political consensus. During this period, aviation was dominated by the arrival of the Jet Age. In civil aviation the jet engine allowed a huge expansion of commercial air travel, while in military aviation it led to the widespread introduction of supersonic aircraft.