When can control of an aircraft be officially assumed?

Control of an aircraft can officially be assumed after it is within your area of jurisdiction. This principle is grounded in the structure of air traffic control responsibilities, where each ATC unit has a specific area that it oversees. As soon as an aircraft enters this designated zone, the controller is tasked with ensuring the safe separation and management of that aircraft.

While the other choices reflect different aspects of aircraft operation and communication, they do not align with the defined moment when control is formally transferred to a controller. For example, being airborne or requesting control does not grant authority until the aircraft enters the designated airspace. Similarly, clearance from ATC is crucial for the operation but does not designate the moment of control transfer.