Equator: The largest horizontal circle of a spherical balloon.
Fins: Small fixed aerofoils attached to different parts of aircraft, in order to promote stability; for example, tail fins, skid fins, etc. Fins are often adjustable. They may be either horizontal or vertical.
Flight path: The path of the center of gravity of an aircraft with reference to the earth.
Float: That portion of the landing gear of an aircraft which provides buoyancy when it is resting on the surface of the water.
Fuselage: The elongated structure to which are attached the landing gear, wings and tail. A fuselage is rarely used with pushers; and in general it is designed to hold the passengers.
Gap: The shortest distance between the planes of the chords of the upper and lower planes of a biplane, measured along a line perpendicular to the chord of the lower plane at its entering edge.
Gas Bag: See Envelope.
Glide: To fly without engine power.
Glider: A form of aircraft similar to an airplane, but without any power plant.
When utilized in variable winds it makes use of the soaring principles of flight and is sometimes called a soaring machine.