that military organization of a nation which is primarily responsible for the conduct of air warfare. The air force has the missions of gaining control of the air, supporting surface forces (as by bombing and strafing), and accomplishing strategic-bombing objectives. The basic weapon systems of air forces are such military airplanes as fighters, bombers, fighter-bombers, attack aircraft, reconnaissance craft, and training craft. Since the mid-20th century, the air forces of some of the world's major powers have also operated those nations' contingents of land-based intercontinental ballistic missiles, as well as of nuclear-armed long-range bombers. The army and naval branches of a nation's armed forces may also operate aircraft, but the air force usually remains the prime instrument of a nation's air power. The organization, command structure, and personnel grades within air forces vary from country to country.

Air forces and air warfare are treated in a number of articles in the Macropaedia. For treatment of the history, types, and technological development of military aircraft, see military aircraft. For treatment of tactical and strategic considerations in aerial warfare, see Air tactics (air warfare). Air warfare during the course of World Wars I and II is treated in World Wars (World War I).