AIM Text
- Pilot.
- Acknowledges receipt and understanding of an ATC clearance.
- Reads back any hold short of runway instructions issued by ATC.
- Requests clarification or amendment, as appropriate, any time a clearance is not fully understood or considered unacceptable from a safety standpoint.
- Promptly complies with an air traffic clearance upon receipt except as necessary to cope with an emergency. Advises ATC as soon as possible and obtains an amended clearance, if deviation is necessary.
- Controller.
- Issues appropriate clearances for the operation to be conducted, or being conducted, in accordance with established criteria.
- Assigns altitudes in IFR clearances that are at or above the minimum IFR altitudes in controlled airspace.
- Ensures acknowledgement by the pilot for issued information, clearances, or instructions.
- Ensures that readbacks by the pilot of altitude, heading, or other items are correct. If incorrect, distorted, or incomplete, makes corrections as appropriate.
Source: FAA Aeronautical Information Manual · current edition · paragraph 5-5-2.
Research Notes
AIM 5-5-2 covers Air Traffic Clearance — the regulatory and operational nature of the ATC clearance.
Definition of a clearance: Authorization by ATC for an aircraft to proceed under specified traffic conditions in controlled airspace. The clearance is not permission to violate FAR/AIM rules; it operates within them.
What a clearance is:
- An offer the pilot may accept or reject
- Conditional on the pilot's ability to comply safely
- Binding once accepted (read back)
What a clearance is not:
- Permission to operate an unairworthy aircraft (§ 91.7 always applies)
- Permission to fly below personal minimums for safety
- Authorization to violate any other FAR
The 'unable' response: Pilots may decline a clearance with "unable" + explanation. ATC will work the problem.