Definition
An ATC clearance, typically a heading, that is not closed out with further instructions to return the aircraft to its filed route or to the next fix on its flight plan. The controller issues a vector but does not, at the time of issuance, specify how or when the aircraft will rejoin its route.
Plain English
ATC tells you to fly a heading but doesn't yet tell you how you'll get back on course. You stay on that heading until they give you the next instruction.
Context Anchor
Used in ATC communication and runway-safety discussions, especially when an instruction depends on another aircraft, vehicle, or event happening first.
Derivation
From control systems, where an 'open loop' is a process that does not feed back into itself. Here the 'loop' is the route: the clearance sends the aircraft off-route without yet closing the loop by returning it to the route.
Why Pilots Care
It gives routing flexibility in busy airspace but requires the pilot to stay alert for follow-up instructions to avoid unintended deviations.
Intuition Check
Open loop clearance does not mean a clearance to fly a loop or an open traffic pattern. It means the clearance depends on a later condition instead of an immediate, direct instruction to act now.
Example Sentence 1
Center issued an open loop clearance of heading 270 to get us around the buildups, and we held that heading for almost twenty minutes before they vectored us back toward the airway.
Example Sentence 2
Instead of a full route clearance, the controller issued an open loop to the VOR and then closed it with a heading assignment.