When does separation minima end for IFR aircraft?

The correct answer is that separation minima end for IFR aircraft after the aircraft has touched down. This is because, during the entire flight, separation minima are established to ensure safe distances between aircraft, which are crucial during all phases of flight, including departure, en route, and approach.

Once the aircraft safely touches down on the runway, it is considered to be in a different operational environment where the requirements for vertical and lateral separation typically change. At this point, air traffic control transitions responsibilities as aircraft begin to move on the ground, and the concern for in-flight separation diminishes since the aircraft is no longer in controlled airspace in the same capacity.

Other options suggest ending the separation minima at various phases such as reaching cruising altitude or initiating landing procedures, but these do not reflect the complete picture of air traffic management protocols. For instance, separation minima remain crucial during the landing phase to prevent conflicts with other landing or departing aircraft until the aircraft is on the ground. Similarly, exiting controlled airspace doesn't coincide with the end of separation minima because the aircraft might still be in transit after landing or taxiing, where safe distances must still be maintained.