Definition
A specified altitude or height in a precision approach or approach with vertical guidance at which the pilot must initiate a missed approach if the required visual reference to continue the approach has not been established. Decision Altitude (DA) is referenced to mean sea level. Decision Height (DH) is referenced to the threshold elevation. The ICAO definition is the international standard adopted by the International Civil Aviation Organization and used by member states for harmonized approach procedures.
Plain English
On certain instrument approaches, this is the point on the way down where you must decide: if you can see the runway environment, you keep flying down to land; if you cannot, you immediately 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 procedures, especially approaches that guide the aircraft down a vertical path toward the runway.
Derivation
The ICAO label means this is the international version of the term, agreed by the International Civil Aviation Organization so that the same approach concepts work the same way across countries. 'Decision' is used because the pilot must make a clear go/no-go choice at that exact point — there is no drifting lower while making up your mind.
Why Pilots Care
It sets the last safe point to continue an approach; passing it without visual contact requires an immediate missed approach to avoid controlled flight into terrain.
Intuition Check
Do not read “decision” as a loose judgment call that can be delayed. At Decision Altitude or Decision Height, the required visual references are either there and you continue, or they are not and you begin the missed approach.
Example Sentence 1
Approaching the DA on the ILS, the captain called the runway lights in sight and continued to land.
Example Sentence 2
The approach chart listed a decision height of 250 feet, so the crew began the climb when no runway environment was visible at that point.