Plain English Meaning

The four basic things an airplane does: fly level, turn, go up, and come down. Everything else is just a mix of these.

Full Definition

The four basic flight maneuvers on which all airplane control is built: straight-and-level flight, turns, climbs, and descents. Every other maneuver a pilot performs is a combination or refinement of these four.

Context Anchor

Seen at the start of basic flight training, especially when learning how the flight controls affect the airplane.

Derivation

Fundamental' comes from the Latin fundamentum, meaning 'foundation.' These four maneuvers are called fundamentals because every other maneuver is built on top of them.