Plain English Meaning

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.

Full 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 or 1,000 feet AGL in conditions). An unstable approach is the trigger for a .