Plain English Meaning

The airplane is set up with everything tucked in -- wheels up (if they retract) and flaps up -- so the wings and body are smooth with nothing sticking out into the airflow.

Full Definition

The aerodynamic state of an airplane in flight with the landing gear retracted (if retractable) and the flaps fully retracted, so that no high-drag devices are extended from the wings or fuselage.

Context Anchor

Seen in slow flight, stall, takeoff, climb, cruise, and discussions when the describes how the airplane is set up for the or .