Definition
An imaginary line running lengthwise down the middle of a runway, taxiway, or aircraft structure, used as a reference for alignment, marking, and design. On runways and taxiways, it is marked with painted stripes (and sometimes lights) that pilots use to keep the aircraft aligned during taxi, takeoff, and landing.
Plain English
A line down the exact middle of something — like a runway or taxiway — that pilots use to stay properly lined up.
Context Anchor
Seen in airport markings, airport diagrams, and airport notices where runway or taxiway alignment is being described.
Derivation
Simply 'center' + 'line' — the line through the center. Worth noting because in aviation, CL refers to a specific physical or geometric reference, not just any middle line.
Why Pilots Care
Maintaining alignment with the centerline ensures proper aircraft positioning on the runway or taxiway, reducing the risk of runway excursions or taxiway deviations.
Intuition Check
Centerline does not mean just any line near the middle of a drawing. In aviation, it means the intended middle path of a runway, taxiway, or similar surface that pilots use for alignment.
Example Sentence 1
After lining up on runway 27, the pilot held the centerline with rudder as airspeed increased on the takeoff roll.
Example Sentence 2
During landing, the instructor reminded the student to track the runway centerline with small corrections.