: For aircraft flying at relatively low speeds and over short distances, these factors are negligible and "lost in the noise" of larger effects like wind and turbulence.
: Removing variables for the Earth's curvature and rotation (Coriolis effect) makes the equations manageable. NASA Flat Non Rotating Earth pdf
NASA reports like Reference Publication 1207 (1988) and Technical Paper 2835 (1989) use these assumptions to linearize aircraft equations of motion. By treating the Earth as a flat, stationary plane, engineers can: : For aircraft flying at relatively low speeds
: Historical reports were written when computer power was limited; simplifying the model allowed for faster simulations. Common Misinterpretations NASA Flat Non Rotating Earth pdf