London has six airports. Which one counts as London?

If someone tells you their flight lands in London, they have told you less than they think. London has six airports with scheduled service — Heathrow, Gatwick, Stansted, Luton, City and Southend — spread across an area more than 100km wide.

This is not a London problem. It is everywhere, and it makes "which city does this flight go to?" a much less obvious question than it appears.

The three answers

Ask where London Luton Airport is and you can get three defensible answers.

Luton. The airport is in Luton, a town in Bedfordshire, and the local council would like a word with anyone who says otherwise.

London. Almost every passenger who lands there is going to London. The airline sells it as London. The airport's own name says London.

Neither, exactly. It is a regional airport that serves a catchment including both, and the honest answer depends on who is asking.

The aviation industry settled this with IATA metropolitan area codes. London gets the code LON, which covers all six airports; New York gets NYC, covering JFK, LaGuardia and Newark. Search for a flight to LON and you get all six.

The awkward cases

The grouping is a judgement call, and some of the calls are strange.

Newark is in New Jersey, not New York — a different state, with its own city around it. It is grouped with New York because that is where its passengers go.

Frankfurt Hahn is about 120km from Frankfurt, in the Hunsrück hills. It was named for the city it markets itself to, not the one it is near. Passengers face roughly a two-hour bus ride.

Milan Bergamo is 45km from Milan and sits beside Bergamo, a substantial city in its own right, which many travellers never see.

Stockholm Skavsta is nearly 100km away, in Nyköping.

There is a whole category of these: airports named after a large city they are merely near, a naming convention popularised by low-cost carriers in the 1990s. The name is a marketing claim about catchment, not a statement of geography.

Why we grouped them

Where To asks you to name where a flight took off and where it is going, and we had to pick a rule. We score against the metropolitan area, not the airport's own town.

The reasoning is about what the game is actually about. The fantasy is "that plane is going to New York" — not "that plane is going to a field in New Jersey". If you correctly work out that an aircraft overhead is bound for New York, being marked wrong because the answer was technically Newark would be infuriating, and would teach you nothing worth knowing.

It also makes the answer space tractable. Around 3,000 airports with scheduled service collapse into a much smaller number of places that people have actually heard of — which matters, because a puzzle whose answer is an airport nobody could name is not hard, it is broken.

So in Where To, Luton and Stansted are both London. Newark is New York. Bergamo is Milan. Hahn is Frankfurt.

The exact airport is still worth knowing, and if you name it you get credit for it. But you will never lose a round for saying London about a flight that landed at Luton — because everyone on board would have said the same thing.