Every incoming aircraft is scheduled to arrive as one flight number and depart as another. The plane lands, goes to a gate, and unloads its passengers and luggage. It must be cleaned, possibly refuelled, and safety inspected, and it may require a new crew. Meals have to be delivered in containers that match the galley configuration of the particular aircraft. Passengers must be rounded up, and in some instances tracked down.
Luggage is loaded and matched to the passenger list.
It's a drill that staff repeat several hundred times a day. GTAA monitors local weather and determines available runway. Pilot instructed by ACC on direction of final approach. ACC transfers responsibility of aircraft to the tower. Tower's Departure and Arrivals Controller clears the pilot for landing.