Open Loop Clearance
|Term||Open Loop Clearance|
an ATC clearance that does not include a specified or implied point where the restriction on the trajectory ends.
SESAR Consortium (2007) CONOPS Acronyms and Definitions, Task 2.2.2 - Milestone 3, Document Number: DLT-0612-222-02-00
Most tactical clearances take this form; they include heading (including track offset), level, and speed restrictions and exceptionally could also cover rates of climb or descent. Open-loop clearances are cancelled (closed) by a further instruction from the controller that defines how the flight should revert to the Reference Business Trajectory (RBT).