Definition
On a precision or approach-with-vertical-guidance instrument approach, the specified altitude (Decision Altitude, referenced to mean sea level) or height (Decision Height, referenced to the threshold elevation) at which the pilot must decide whether to continue the approach to landing or execute a missed approach. The decision must be made by the time the aircraft reaches this point on the glidepath; if the required visual references for the runway are not in sight, a missed approach must be initiated.
Plain English
It's the point on an instrument approach where you have to make a call: if you can see enough of the runway to land safely, you keep going. If you can't, you go around. DA is given as a height above sea level; DH is given as a height above the runway.
Context Anchor
Seen on instrument approach charts and used during approach briefings before flying to a runway in low visibility or low clouds.
Derivation
From Latin decidere, meaning 'to cut off' or 'settle.' At this altitude or height, the choice is cut off — you either continue or go missed. There is no in-between.
Why Pilots Care
Reaching DA/DH without visual references means the approach must be abandoned to avoid terrain or runway incursions.
Grounding Statement
Picture flying down through cloud on an approach: at DA/DH, you either have the runway environment in sight and can land safely, or you begin the missed approach.
Intuition Check
Decision does not mean you can keep thinking about it after passing the point. At DA/DH, the decision must already be made: continue only if landing is safe and the required visual references are in sight; otherwise go missed. Altitude and height are not the same here: altitude is measured from mean sea level, while height is measured from the runway threshold elevation.
Example Sentence 1
Approaching DA on the ILS, the captain called the runway environment in sight and continued to land.
Example Sentence 2
Because the runway was still obscured at decision height, the crew flew the published missed approach.