Definition
An authorization issued by air traffic control (ATC) for a pilot to proceed under instrument flight rules (IFR), specifying the route, altitude, and any restrictions the pilot must follow. The clearance must be read back to the controller and complied with once accepted.
Plain English
Permission from air traffic control to fly a specific route and altitude under instrument flight rules. The pilot reads it back to confirm they heard it correctly, then flies what was cleared.
Context Anchor
A pilot may receive an instrument clearance before departure, while changing from visual flying to instrument flying, or before flying an instrument approach.
Derivation
‘Clearance’ comes from ‘clear’ — meaning the way ahead is open and approved. In ATC use, it means the controller has cleared the airspace and procedure for the pilot to use. ‘Instrument’ refers to flying by reference to cockpit instruments rather than by looking outside, which is the regime this clearance authorizes.
Why Pilots Care
It provides the legal route and altitude instructions needed for safe, compliant IFR flight and prevents airspace conflicts.
Intuition Check
Do not read clearance as simply “there is space ahead.” In this context, clearance means official permission with instructions attached. Do not read instrument as a cockpit gauge by itself. Here it means flying under instrument flight rules.
Example Sentence 1
Before taxiing for an IFR departure, the pilot called clearance delivery and copied the instrument clearance word for word.
Example Sentence 2
In low ceilings the instructor advised the student to request an instrument clearance rather than attempting a visual departure.