Definition
Unplanned departures from a target altitude or airspeed during flight, occurring when the pilot allows the aircraft to drift outside the intended values without recognizing or correcting the change in time.
Plain English
Drifting off your chosen altitude or airspeed without meaning to. The numbers change while you're focused on something else, and you didn't catch it.
Context Anchor
Seen in basic flight training when learning to hold a steady altitude and airspeed during climbs, descents, turns, and straight-and-level flight.
Derivation
Deviation comes from Latin words meaning “to turn away from the path.” In aviation, it means moving away from the value or condition you intended to hold, such as a selected altitude or airspeed.
Why Pilots Care
Uncorrected deviations can quickly erode situational awareness, increase pilot workload, waste fuel, and lead to entry into unsafe flight conditions.
Intuition Check
Do not read “deviation” as only a rule violation. Here it simply means the airplane has moved away from the altitude or airspeed the pilot intended to maintain.
Example Sentence 1
Dividing attention between the chart and the radio led to unintentional altitude-airspeed deviations that the instructor had to point out.
Example Sentence 2
The instructor stressed that minimizing unintentional altitude-airspeed deviations leads to smoother, more efficient cross-country legs.