Definition
A final approach in which one or more key parameters — airspeed, descent rate, glidepath, configuration, power setting, or alignment with the runway centerline — fall outside the established limits for a safe landing, and are not corrected by a defined gate (typically 500 feet AGL in visual conditions or 1,000 feet AGL in instrument conditions). An unstable approach is the trigger condition for a go-around.
Plain English
An approach where the airplane is not on speed, on path, on heading, and properly configured to land, with the corrections needed becoming too large or too late to safely fix before touchdown.
Context Anchor
You will hear this term during landing training, approach briefings, safety discussions, and any decision about whether to continue landing or climb away and try again.
Derivation
Unstable comes from stable, meaning firm or steady, with un- meaning not. Approach means coming nearer. In aviation, the phrase points to a landing attempt that is not steady enough as the airplane gets close to the runway.
Why Pilots Care
Continuing an unstable approach raises the risk of runway excursion, hard landing, or loss of control.
Grounding Statement
Picture the airplane close to the runway while speed, height, and alignment are still changing instead of settling down.
Intuition Check
Unstable does not mean the airplane is out of control. It means the approach is not steady and within safe limits soon enough to continue safely to landing.
Example Sentence 1
Crossing 500 feet still 20 knots fast and high on the glidepath, the pilot called the approach unstable and initiated a go-around.
Example Sentence 2
Stabilized approach training teaches pilots to reject any unstable approach rather than attempt to fix it late in the landing.