Before pushback: clearance and ground control
The flight begins on the radio before the aircraft moves. The crew calls clearance delivery — or receives a digital datalink clearance — confirming the route, initial altitude and the four-digit transponder "squawk" code that will identify the flight on radar screens from that moment on.
The flight begins on the radio before the aircraft moves. The crew calls clearance delivery — or receives a digital datalink clearance — confirming the route, initial altitude and the four-digit transponder "squawk" code that will identify the flight on radar screens from that moment on.
After pushback, ground control takes over, issuing taxi instructions across the airport's taxiway network: a series of letters and hold-short points that routes the aircraft to the departure runway without conflicting with other traffic. At big airports like Heathrow this taxi phase alone can take 15–25 minutes and involves careful choreography between dozens of aircraft.
Tower and departure
At the runway, the crew switches to the tower frequency. The tower controller owns the runways: nothing lands or departs without their explicit clearance. "Cleared for takeoff" is one of the most protected phrases in aviation — read back by the crew, and never ambiguous.
At the runway, the crew switches to the tower frequency. The tower controller owns the runways: nothing lands or departs without their explicit clearance. "Cleared for takeoff" is one of the most protected phrases in aviation — read back by the crew, and never ambiguous.
Seconds after liftoff, the aircraft is handed to departure control (part of the approach radar unit). The departure controller climbs the aircraft away from the airport along a standard instrument departure route, threading it between other arrivals and departures in some of the busiest airspace in the world. At Heathrow, spacing departures behind wake-turbulence "heavy" aircraft is a constant part of the puzzle.
En route: area control and the ocean
Once clear of the terminal area, the flight passes to area control — in the UK, NATS centres at Swanwick and Prestwick — which manage aircraft along the airway network at cruise altitude, handing the flight from sector to sector and country to country. Each handover is a frequency change: "Speedbird 117, contact London 132.6".
Once clear of the terminal area, the flight passes to area control — in the UK, NATS centres at Swanwick and Prestwick — which manage aircraft along the airway network at cruise altitude, handing the flight from sector to sector and country to country. Each handover is a frequency change: "Speedbird 117, contact London 132.6".
Westbound over the North Atlantic there's no radar, so the system changes. Flights follow organised tracks published twice daily based on the jet stream — the North Atlantic Tracks — separated by time, altitude and position reports via satellite and datalink. Shanwick Oceanic, based in Prestwick, manages the eastern half. It's procedural control: careful, pre-planned separation rather than a radar picture.
Arrival: approach, tower and the gate
Descent into New York reverses the sequence. Approach control sequences arrivals into a flowing queue — issuing vectors and speed instructions, and if the airport is saturated, assigning holding patterns. When the pilot announces "we've been asked to hold", it's the approach controller managing demand, not a fault with the aircraft.
Descent into New York reverses the sequence. Approach control sequences arrivals into a flowing queue — issuing vectors and speed instructions, and if the airport is saturated, assigning holding patterns. When the pilot announces "we've been asked to hold", it's the approach controller managing demand, not a fault with the aircraft.
Established on final approach, the flight goes to JFK tower for landing clearance, then to ground control for the taxi to the stand. One flight, five or more distinct controllers, each responsible for one slice of the journey — the handovers are the system working as designed.
When it goes wrong
Controllers are also the first line when a flight has a problem. A crew declaring "pan-pan" (urgency) or "mayday" (distress) immediately gets priority: airspace is cleared, the most direct routing is offered, and airports prepare emergency services. Squawk codes 7700 (emergency), 7600 (radio failure) and 7500 (unlawful interference) alert every controller watching, even without a word on the radio.
Controllers are also the first line when a flight has a problem. A crew declaring "pan-pan" (urgency) or "mayday" (distress) immediately gets priority: airspace is cleared, the most direct routing is offered, and airports prepare emergency services. Squawk codes 7700 (emergency), 7600 (radio failure) and 7500 (unlawful interference) alert every controller watching, even without a word on the radio.