When does a departure clearance become effective?

A departure clearance becomes effective upon termination of the call with Air Traffic Control (ATC). This means that once the pilot has received and acknowledged the clearance and the communication with ATC has concluded, the clearance is considered in effect.

This procedure ensures that pilots are fully aware of their clearance before departing. It also provides a clear moment when the pilot can start acting on the clearance, which is essential for maintaining organized and safe airport operations. The timing of the clearance being effective is crucial because it allows pilots to take into account any changes or final instructions that may have been communicated during the conversation with ATC.

The other options do not accurately capture when the clearance is valid. A flight plan, while important, does not confirm the acceptance of clearance; the aircraft's engine initiation does not signify the clearance's effectiveness, as the pilot may still be awaiting instructions; and issuing the clearance alone does not mean it is effective until communication has concluded.