What are military aircraft?

A military aircraft is a state aircraft used by the armed forces, crewed by military personnel and bearing its country's nationality markings. That status carries legal consequences: the 1944 Chicago Convention, which governs international civil aviation, expressly excludes military, customs and police aircraft, so they cannot overfly or land in another state without authorisation and are not subject to civil certification rules. That's why a transport derived from a commercial aircraft, such as the A330 MRTT or the KC-46, ceases to be civilian the moment it is registered as a state aircraft.

Missions fall into a few categories. Combat: fighters to achieve air superiority, attack aircraft and bombers to strike targets on land or at sea. Support: troop and cargo transport, aerial refuelling, airborne early warning with onboard radar, electronic warfare, maritime patrol and anti-submarine warfare, reconnaissance and search and rescue. Training: basic and advanced trainers in which pilots learn before moving on to operational aircraft. To these are added helicopters and, for the past two decades, unmanned systems, which already carry out much of the surveillance and a growing share of strikes.

An airliner's priority is to carry passengers safely at the lowest cost; a military aircraft's is to complete the mission and survive. That translates into tougher structures, redundant systems, impact protection, countermeasures, encrypted communications and, in fighters, cockpits with ejection seats. Their service life is long, often 30 to 40 years, and maintenance absorbs most of the total cost, far more than the purchase price.