An air force is the branch of a country's military that operates aircraft for defense and warfare. While armies fight on land and navies fight at sea, air forces control the skies. They fly fighter jets to protect their country's airspace, bombers to strike enemy targets, cargo planes to transport troops and supplies, and helicopters for rescue missions.

The United States Air Force, for example, trains pilots, maintains thousands of aircraft, and operates bases around the world. During World War II, air forces became crucial to military strategy: controlling the air often meant winning the battle below. Before countries had dedicated air forces, armies and navies operated their own smaller aviation units.

Modern air forces do more than fight. They help during natural disasters by delivering emergency supplies, search for missing people, and even study weather patterns. Some air force pilots fly so high and fast that they experience forces that would make most people pass out, which is why they train intensively and wear special flight suits.

The term can also refer simply to a group of military aircraft, as in “The general commanded a powerful air force of bombers and fighters.” Creating an effective air force requires skilled pilots, engineers, mechanics, air traffic controllers, and countless others who keep these complex machines flying safely.