| 01 | 
Aerodynamics | 
Flight characteristics and problems of full-scale or model aircraft and their components as they are affected by the dynamics of air; Flight testing and wind tunnel testing. Includes theoretical and experimental aerodynamics as applied to missiles, See 16/02/01, Guided Missile Dynamics, Configurations and Control Surfaces. For the behavior of spacecraft in air, see 22/03, Spacecraft Trajectories and Reentry. For the aerodynamics of ground structures, see 13/13, Structural Engineering and Building Technology. | 
| 02 | 
Military Aircraft Operations | 
Military aircraft operations such as takeoff Operations and landing, air traffic, all weather and night flight, taxiing, approach, and inflight refueling; Flight safety; Ground safety; Aviation accident studies; Aircraft simulators and training devices. For missile operations, see Field 16, Guided Missile Technology. For spacecraft operations, See Field 22,  Space Technology. For navigation and air traffic control, see 17/07/03,  Air Navigation and Guidance. | 
| 03 | 
Aircraft | 
Design, production, and maintenance of aircraft, aircraft components, and aircraft equipment; Structural studies of complete aircraft components such as airframes, bodies, and wings. Airworthiness; Crashworthiness; Aircraft damage assessment and vulnerability studies; effects of gunfire and blast on aircraft and flight equipment. For civilian aircraft, See 01/03/09,  Civilian Aircraft. For specific types of aircraft, See subgroups 01/03/01 - 01/03/12. See also Field 16,  Guided Missile Technology and Field 22,  Space Technology. | 
| 03/01 | 
Helicopters | 
Includes attack helicopters. For civilian helicopters, See 01/03/09,  Civilian Aircraft. | 
| 03/02 | 
Bombers | 
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| 03/03 | 
Attack and Fighter Aircraft | 
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| 03/04 | 
Patrol and Reconnaissance Aircraft | 
Includes observation aircraft. | 
| 03/05 | 
Transport Aircraft | 
Includes tanker aircraft. | 
| 03/06 | 
Training Aircraft | 
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| 03/07 | 
V/STOL | 
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|  03/08 | 
Gliders and Parachutes | 
Includes paragliders and kites, for both military and civilian applications. | 
| 03/09 | 
Civilian Aircraft | 
Does not include aircraft modified for military use. | 
| 03/10 | 
Pilotless Aircraft R.P.V.; Drones. | 
Includes full size aircraft when configured as drones. | 
| 03/11 | 
Lighter-than-air Aircraft | 
Airships, blimps, dirigibles, balloons, for both civilian and military applications. | 
| 03/12 | 
Research and Experimental Aircraft | 
Includes aerospace aircraft. | 
| 04 | 
Flight Control and Instrumentation | 
Instruments, sensors, displays and recorders necessary for control and monitoring the flight of an aircraft; Cockpit and cabin display devices and onboard checkout systems; Onboard navigation display devices; Automatic pilots; Stability and control systems; Boundary layer control systems; Dynamic and static control devices. If the application of a flight control system is apparent, see the field where the application is treated. For devices used to compute flight times and headings, See 17/07/03, Air Navigation and Guidance. | 
| 05 | 
Terminal Flight Facilities | 
Airports; Military air bases; Runways; Hangars; Ground refueling systems; Heliports; Aircraft handling and maintenance equipment; Taxiways; Parking aprons; Crash and fire facilities. For air traffic control systems, See 17/07/03, Air Navigation and Guidance. | 
|  06 | 
Commercial and General Aviation | 
Civil aircraft operations, as described in 01/02. Also includes civil airport passenger and vehicle traffic studies. |