I.

Introduction

Aviation, term applied to the science and practice of flight in heavier-than-air craft, including airplanes, gliders, helicopters, ornithopters, convertiplanes, and VTOL (vertical takeoff and landing) and STOL (short takeoff and landing) craft (see Airplane; Glider; Helicopter). These are distinguished from lighter-than-air craft, which include balloons (free, usually spherical; and captive, usually elongated), and dirigible airships (see Airship; Ballooning).

Operational aviation is grouped broadly into three classes: military aviation, commercial aviation, and general aviation. Military aviation includes all forms of flying by the armed forces—strategic, tactical, and logistical. Commercial aviation embraces primarily the operation of scheduled and charter airlines. General aviation embraces all other forms of flying such as instructional flying, crop dusting by air, flying for sport, private flying, and transportation in business-owned airplanes, usually known as executive aircraft.