Definition
An ATC phrase used when a pilot is told to expect a delay of unknown duration. Controllers use this wording when traffic, weather, equipment, or runway conditions prevent them from issuing a specific Expect Further Clearance (EFC) time. When the cause is known, the controller will state the reason; if an estimated clearance time can be determined, it will be passed to the pilot as soon as possible.
Plain English
ATC is telling you that you'll be delayed, but they can't say for how long yet. If they know why, they'll tell you. If they figure out roughly when you can expect to go, they'll let you know.
Context Anchor
Heard in radio communications when air traffic control cannot issue an immediate clearance, such as during traffic congestion, weather delays, holding, or airport flow delays.
Why Pilots Care
It lets pilots adjust fuel planning and expectations during uncertain holds instead of assuming a quick release.
Intuition Check
“Indefinite” does not mean the flight is cancelled or forgotten; it means the exact delay length is not known yet. “Expect further clearance” does not mean you are already cleared to continue; it means another clearance or update is expected at the stated time.
Example Sentence 1
After landing was suspended due to a runway inspection, the tower advised the holding aircraft, "Delay indefinite, reason runway closure, expect further clearance time unknown."
Example Sentence 2
After receiving delay indefinite expect further clearance time the crew began calculating extra fuel burn.