When should you call for departure unless otherwise instructed by Tower?

Calling for departure when you are number one or number two at the hold short line is the correct approach because it aligns with standard operating procedures and ensures effective communication with Air Traffic Control (ATC). At this point, you are in the final stages of your preparation to depart, allowing ATC to manage traffic efficiently and provide clearance for takeoff.

Being number one or two indicates readiness and proximity to the runway, making it the appropriate scenario to check in with the tower for clearance. It demonstrates adherence to traffic management protocols, allowing for safe sequencing of departures. This is crucial in busy airspace where coordination between departing and arriving aircraft is critical to maintaining safety and efficiency.

While calling at the gate might seem logical to some, it does not provide ATC with the necessary situational awareness regarding the specific timing of your departure. Waiting for a clearance while still taxiing without being at the hold short line may also cause unnecessary delays. Making the call at the correct position supports a smooth transition from ground to flight operations.