Plain English Meaning

If you drew a straight line out from the end of the runway, continuing in the same direction the runway points, that line is the runway centerline extension. Pilots use it as an invisible track to fly along when landing or departing.

Full Definition

An imaginary line projected outward from each end of a runway along the same heading as the runway centerline, used as a reference for aligning the aircraft on final approach and after takeoff.

Context Anchor

Used when flying the traffic pattern, especially when turning toward final approach or tracking straight out after takeoff.

Derivation

Centerline means the line through the middle of something. Extension comes from a word meaning to stretch out. Together, the phrase means the runway’s middle line continued outward beyond the actual runway.