Definition
The fourth leg of the standard airport traffic pattern, flown perpendicular to the landing runway after the downwind leg and before turning onto final approach. The aircraft descends on base leg while configuring for landing.
Plain English
The short, crosswise leg flown just before turning to line up with the runway for landing. It connects the downwind leg (parallel to the runway) to the final leg (straight in to land).
Context Anchor
Used when describing the legs of a standard airport traffic pattern, especially during landing practice and radio calls near an airport.
Derivation
From the everyday word 'base,' meaning a foundational or supporting position. In the traffic pattern, it's the leg that sets up — or forms the base for — the final approach.
Why Pilots Care
Correct base leg positioning provides proper spacing from other aircraft and allows a stabilized descent to the runway.
Intuition Check
Base does not mean a home airport, a military base, or the bottom of something here. In a traffic pattern, base means the pattern leg between downwind and final.
Example Sentence 1
Tower instructed the pilot to report turning base for runway 27.
Example Sentence 2
While on base the student pilot maintained altitude and airspeed to avoid overshooting the final approach course.