1. the operation of aircraft
2. the aircraft industry

Examples

• She studied aviation in college and became a pilot.
• The aviation industry has grown rapidly over the past century.
• Safety regulations in aviation are extremely strict.
• He works in aviation maintenance at the airport.
• The museum displays the history of aviation from the Wright brothers to modern jets.
• Aviation fuel prices affect airline operating costs.
• Military aviation played a crucial role in the war.