Plain English Meaning
If you mentally draw the runway's center stripe out into the sky past the end of the runway, that invisible line is the extended centerline. Pilots aim to fly along it when lining up to land.
Full Definition
An imaginary line projected straight out from a runway's centerline, beyond the runway threshold, used as a reference for aligning the aircraft on final approach.
Context Anchor
Commonly encountered in airport traffic pattern work, especially when turning from base leg to final approach.
Derivation
“Extended” comes from the idea of stretching something outward, and “centerline” means a line through the middle. Together, the term means the runway’s middle line stretched outward beyond the runway itself.
Why Pilots Care
Maintaining the extended centerline ensures proper runway alignment, safe spacing from other , and reduces the chance of or unstabilized .