Definition
Airports that have been formally closed for an indefinite period, with no scheduled reopening date. These airports are removed from active use and are not maintained or monitored to the standards of an operational airport. They are depicted on aeronautical charts and listed in the Chart Supplement with a notation indicating their closed status, and runways are typically marked with a large yellow X to visually warn pilots from above that the surface is not available for landing or takeoff.
Plain English
These are airports that have been shut down for an unknown length of time, with no announced plan to reopen. They still appear on charts so pilots know they exist, but they are not safe or legal to use, and the runways are marked with a yellow X to make that clear from the air.
Context Anchor
Seen in FAA chart and procedure discussions where airport availability affects instrument planning, approach use, and alternate selection.
Derivation
"Indefinitely" comes from the Latin in- ("not") and definire ("to set limits"). It means the closure has no fixed end. The airport is closed, and no date has been set to reopen it.
Why Pilots Care
Attempting to land at one creates serious safety risks and may violate regulations.
Intuition Check
Do not read “indefinitely” as “permanently.” It means “for an unknown amount of time,” so the airport stays off your usable list until current official information shows otherwise.
Example Sentence 1
While reviewing the Chart Supplement, the pilot noticed the nearest field was listed as closed indefinitely and removed it from the list of possible alternates.
Example Sentence 2
Runway damage caused the field to be marked closed indefinitely on the updated chart.