Plain English Meaning
One of the airplane's engines has stopped working, and the airplane is flying on the engine or engines that are still running.
Full Definition
A condition in a multiengine airplane in which one engine has failed or been intentionally shut down while the remaining engine or engines continue to provide thrust. OEI is used to describe performance, handling, and procedures that apply specifically when a multiengine airplane is operating without all engines producing power.
Context Anchor
Seen in multiengine airplane training, performance charts, emergency procedures, and discussions of engine failure after takeoff.
Why Pilots Care
It reduces climb performance and thrust, making obstacle clearance and more demanding, especially .