What action must a pilot take prior to deviating from an air traffic clearance?

Before a pilot can deviate from an air traffic clearance, it is essential to notify Air Traffic Control (ATC) about the deviation. This action is crucial for maintaining safety and coordination in the airspace. When a pilot informs ATC of any changes to their intended flight plan, it allows ATC to provide updated instructions, manage other aircraft in the vicinity, and maintain overall situational awareness.

Failing to communicate a deviation may lead to conflicts with other aircraft, as ATC relies on clear and accurate information to ensure safe separation. By notifying ATC, the pilot ensures that all operations within the controlled airspace remain orderly and safe, aligning with regulations and best practices in aviation.