When is ATC clearance deviation allowed?

• A. Emergency, TCAS RA compliance, amended clearance
• B. During routine operations
• C. When the pilot requests deviation
• D. Only when the dispatcher approves

Answer: (A)

Safety actions take precedence when a clearance must be deviated from. Deviation from an ATC clearance is permitted only in three situations: in an emergency, to comply with a TCAS resolution advisory, or when ATC issues an amended clearance that supersedes the earlier instruction. In an emergency, immediate maneuvering to preserve the aircraft and passengers is paramount, even if it conflicts with the existing clearance. If a TCAS RA is active, you must follow the RA instructions right away to avoid a collision, then coordinate with ATC as soon as practical after.

If ATC provides an amended clearance, that new instruction overrides the previous one, so you may diverge from the original clearance to comply with the amended one. In routine operations, or based on pilot request without a safety-driven amendment, deviation from clearance is not allowed.