Gives basic definitions and deals with motion relative to the atmosphere, assumed to be at rest or in translational motion at constant velocity relative to the Earth. The aircraft is assumed to be rigid. However, most of the definitions can be applied to the case of a flexible aircraft. Describes axis systems, angles, velocities and angular velocities, aircraft inertia, forces, moments, coefficients and load factors, thrust, resultant moment of propulsive force, coefficients thereof, control forces and moments, motivators and their forces and moments.