At Heathrow, a 09:15 departure to JFK isn't a time. It's a property right.
British Airways will operate 50 daily flights to US destinations this summer — its largest transatlantic schedule ever, departing from both Heathrow and Gatwick. The announcement reads like a demand story. It isn't. It's a geometry problem.
Heathrow runs at roughly 98% slot utilization. The airport operates as a Level 3 coordinated facility under IATA's framework, meaning every single movement — takeoff or landing — requires a pre-allocated slot. There is no spare capacity to absorb new frequencies through organic growth. If BA wants to add a US route at Heathrow, it must acquire a slot from another carrier, or pull one from an existing BA service elsewhere in its network.
BA holds approximately half of all Heathrow slots — the largest single portfolio at any airport in the world. That dominance is the product of grandfather rights: the rule that carriers who operated a slot in the previous equivalent season retain it the following year, provided they used it at least 80% of the time. This use-it-or-lose-it mechanism is why airlines sometimes fly near-empty aircraft on thin routes. The slot is worth more than the revenue. Surrendering it means surrendering it permanently.
So when BA maps its "record" US network, what it's really mapping is decades of accumulated slot rights, carefully reallocated toward the highest-yielding markets. Every transatlantic frequency that exists at Heathrow displaced something else.
Gatwick serves as the pressure valve. It offers genuine capacity flexibility that Heathrow cannot. But it carries a yield penalty — business travelers, who drive transatlantic profitability, overwhelmingly prefer Heathrow's connectivity and terminals. Gatwick transatlantic routes work. They just work harder for lower margins.
Fifty daily departures to America. The ceiling was always the constraint — demand simply filled whatever shape it allowed.