AIM Text
- A clearance issued by ATC is predicated on known traffic and known physical airport conditions. An ATC clearance means an authorization by ATC, for the purpose of preventing collision between known aircraft, for an aircraft to proceed under specified conditions within controlled airspace. IT IS NOT AUTHORIZATION FOR A PILOT TO DEVIATE FROM ANY RULE, REGULATION, OR MINIMUM ALTITUDE NOR TO CONDUCT UNSAFE OPERATION OF THE AIRCRAFT.
- 14 CFR section 91.3(a) states: “The pilot-in-command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft.” If ATC issues a clearance that would cause a pilot to deviate from a rule or regulation, or in the pilot's opinion, would place the aircraft in jeopardy, IT IS THE PILOT'S RESPONSIBILITY TO REQUEST AN AMENDED CLEARANCE. Similarly, if a pilot prefers to follow a different course of action, such as make a 360 degree turn for spacing to follow traffic when established in a landing or approach sequence, land on a different runway, takeoff from a different intersection, takeoff from the threshold instead of an intersection, or delay operation, THE PILOT IS EXPECTED TO INFORM ATC ACCORDINGLY. When the pilot requests a different course of action, however, the pilot is expected to cooperate so as to preclude disruption of traffic flow or creation of conflicting patterns. The pilot is also expected to use the appropriate aircraft call sign to acknowledge all ATC clearances, frequency changes, or advisory information.
- Each pilot who deviates from an ATC clearance in response to a Traffic Alert and Collision Avoidance System resolution advisory must notify ATC of that deviation as soon as possible.
- When weather conditions permit, during the time an IFR flight is operating, it is the direct responsibility of the pilot to avoid other aircraft since VFR flights may be operating in the same area without the knowledge of ATC. Traffic clearances provide standard separation only between IFR flights.
Source: FAA Aeronautical Information Manual · current edition · paragraph 4-4-1.
Research Notes
AIM 4-4-1 introduces ATC clearances — the formal authorization from ATC that permits an aircraft to operate in controlled airspace under specific conditions.
What an ATC clearance is: An authorization to proceed under specified traffic conditions in controlled airspace. The clearance is NOT permission to disregard regulations — § 91.3(a) keeps the PIC as the final authority. The pilot must comply with the clearance per § 91.123, OR declare emergency per § 91.3(b), OR refuse the clearance with "unable."
The full IFR clearance — CRAFT format: A standard IFR clearance contains:
- Clearance limit (typically the destination airport, sometimes an intermediate fix)
- Route ("as filed" or specific airways/fixes)
- Altitude (initial cruising altitude or "expect [altitude] [time] after departure")
- Frequency (departure control frequency)
- Transponder (squawk code)
Pilot's readback obligation: Per § 91.123(b), read back any clearance when requested. The pilot's readback must include: assigned heading, assigned altitude, route changes, frequency assignments, and any other controllable items.
The 'unable' response: If the pilot cannot comply with a clearance (aircraft can't achieve the assigned altitude, fuel is insufficient for the route, weather is unsafe), the pilot says "unable" and requests an alternative. ATC will work the problem.
Reference: § 91.123 (compliance with ATC clearances); § 91.3 (PIC authority); AIM 4-4-1.