When should civil and military transport aircraft be instructed to "contact departure" after takeoff?

The appropriate time for civil and military transport aircraft to be instructed to "contact departure" after takeoff is when they are 1/2 mile beyond the runway end. This instruction is typically given to ensure that the aircraft has safely cleared the runway environment and is in a position to transition from the local control of the tower to the departure control, which manages aircraft as they continue their ascent and departure from the airport.

In the context of air traffic control operations, this distance provides a buffer for separation between departing aircraft and those that may still be in the vicinity of the airport. The timing is essential for maintaining safe operations and ensuring that the aircraft can proceed on its intended flight path without conflict with other aircraft operations around the airport, such as those transitioning to or from the runway.

While altitude thresholds like 2000 ft AGL are significant in the operational context, they pertain more to airspace classifications and transitions rather than the immediate requirement for contacting departure after takeoff. Therefore, the half-mile distance serves as a more practical guideline in the immediate post-departure phase.