Anti-aircraft warfare or counter-air defence is defined by
In some countries, such as Britain and Germany during the
Until the 1950s, guns firing ballistic munitions ranging from 20 mm to 150 mm were the standard weapons; guided missiles then became dominant, except at the very shortest ranges (as with
The term air defence was probably first used by Britain when
NATO defines anti-aircraft warfare (AAW) as "measures taken to defend a maritime force against attacks by airborne weapons launched from aircraft, ships, submarines and land-based sites." In some armies the term All-Arms Air Defence (AAAD) is used for air defence by nonspecialist troops. Other terms from the late 20th century include GBAD (Ground Based AD) with related terms SHORAD (Short Range AD) and
Non-English terms for air defence include the German FlaK (FliegerabwehrKanone, "aircraft defence cannon", also cited as Flugabwehrkanone), whence English flak, and the Russian term Protivovozdushnaya oborona (
The maximum distance at which a gun or missile can engage an aircraft is an important figure. However, many different definitions are used but unless the same definition is used, performance of different guns or missiles cannot be compared. For AA guns only the ascending part of the trajectory can be usefully used. One term is "ceiling", the maximum ceiling being the height a projectile would reach if fired vertically, not practically useful in itself as few AA guns are able to fire vertically, and maximum fuse duration may be too short, but potentially useful as a standard to compare different weapons.
The British adopted "effective ceiling", meaning the altitude at which a gun could deliver a series of shells against a moving target; this could be constrained by maximum fuse running time as well as the gun's capability. By the late 1930s the British definition was "that height at which a directly approaching target at 400 mph (=643.6 km/h) can be engaged for 20 seconds before the gun reaches 70 degrees elevation". However, effective ceiling for heavy AA guns was affected by nonballistic factors: