What is an air force?

The earliest military aircraft belonged to the army or the navy, treated as just another branch alongside cavalry or artillery. The First World War showed that air warfare had its own rules, and the United Kingdom merged the Royal Flying Corps and the Royal Naval Air Service into the RAF in 1918, the world's first independent air force. The United States did not separate the USAF from the Army until 1947; Spain created the Ejército del Aire in 1939, at the end of the civil war, and in 2022 added "and Space" to its name after taking on space surveillance duties.

Its missions fall into a few families. Air control, with fighters and radars that monitor airspace around the clock and scramble on alert at any unidentified track. Strikes against targets on land or sea, using bombs and guided missiles. Intelligence and reconnaissance, with aircraft, drones and satellites. Air transport and in-flight refuelling, which allow troops to be deployed and distant operations to be sustained. And search and rescue, which in many countries includes disaster relief and firefighting.

The typical structure runs from the squadron to the wing or air base, with an operational command that plans and a personnel and materiel command that sustains. Spain's Ejército del Aire y del Espacio has around 20,000 personnel, Eurofighter and F-18 fighters, A400M transports and A330 MRTT tanker aircraft, and continuously contributes detachments to NATO air policing. Not all military aviation is an air force: navies and armies retain their own helicopter and carrier-based aircraft wings.