Definition
A landing or takeoff area at an airport that is not officially designated, marked, or maintained as a runway, but is sometimes used by pilots for operations such as taxi, takeoff, or landing. Informal runways are not published in official airport diagrams and have no assigned runway number, lighting, or markings.
Plain English
A strip of ground at an airport that pilots sometimes use to take off or land, but which has not been officially set up as a runway. It is not on the airport diagram and does not have a runway number or markings.
Context Anchor
Seen in airport information, especially for small, private, remote, or lightly developed landing areas.
Derivation
Informal comes from the Latin informalis, meaning 'not in proper form.' Here it signals that the surface is used like a runway but has not been formally established as one.
Why Pilots Care
Pilots must personally verify surface suitability, obstacles, and wind without published airport data or visual aids.
Intuition Check
Informal does not mean casual or optional here. It means the runway may be used for aircraft, but it is not formally marked and identified like a standard runway.
Example Sentence 1
The pilot used an informal runway alongside the main strip for short takeoff practice in the light tailwheel aircraft.
Example Sentence 2
Before using the informal runway, the pilot walked the length to check for ruts and debris.