London has five international airports. Does any city have more?
Heathrow, Gatwick, Stansted, Luton…
What’s the fifth one?
London City.
First of all, define “city” - to these airports have to be in the city limits, or just nearby and associated with the city.
Second, define “international airport” - is that one with scheduled passenger service to other countries, one with “international” in the name, or one where customes services for those entering from abroad can be obtained?
Otherwise, this thread could turn into one giant quibble.
OK, associated with the city (otherwise it becomes pretty meaningless). And ‘international’ meaning scheduled international flights. (Otherwise the tally for London probably gets into double figures)
…but on the other hand, quibbles can be good 
…thinking about it, there’s probably going to be major non-international airports in the US. If so, argue your case for inclusion 
I’d be happy to… but right now I have to get down to my (non-)international airport.
The weather’s fine, got buddies to fly with, and since this is 9/11 getting airborne is a little bit a “so THERE!” 
act of defiance towards those who wish us ill.
So I’ll come back to this later.
A few years ago Amsterdam Schiphol was promoting itself as " London’s sixth airport " because so many people , especially from eastern England , were using that airport to access international ( especially transoceanic ) flights. It was much easier for them to fly from Norwich or Humberside airports to Amsterdam rather than battle through the traffic down to Heathrow. Of course this has changed now that there are more flights from Stansted and Luton.
I remember that, Rayne Man - although it seems a long time ago, given that KLM no longer fly to Stansted at all.
OK, so I’ve realised that London sort of has a sixth…there’s a daily hop across to France from London Ashford (which I’d never even heard of before). So I’m adding an extra rule for the sake of meaningfulness, that there has to be more than one daily flight out of the airport 
How about New York City?
You have JFK, LaGuardia and Newark Airports, obviously. Then you can definitely add Westchester County Airport (flights to Canada). You can add possibly MacArthur Airport in Islip, which doesn’t seem to have direct international flights but is a Southwest hub, meaning lots of traffic. And there’s Stewart International Airport. I’m not sure if there are any international flights from there, but it does have international in the name.
Remember that the US is a big country, so even if an airport isn’t international, it may still have a lot of traffic.
If you spread the net a bit wider there is now yet another airport that could be classed as serving London. This is Manston ( near Ramsgate ) where a new cut-price airline has started operations . The airport now calls itself Kent International.
Details of this new airline :- Flight Scan | Cheap Flights, Hotels, Car Rental and Travel
I did mention including non-international ones somewhere earlier
So New York pips London…does anywhere have seven airports?
Living in a border state, one sees “international” in the names of grass runway airports. You can’t drive 20 miles here, without finding an international airfield. Most here, have regular flights for fishermen and hunters to Canada.
Nice I didn’t realise it had acquired a scheduled service.
So, London’s back in the race again …
That’s the kind of one I was discounting when I mentioned Ashford earlier.
Right, so we’ll scratch ‘international’ from the question and start looking for, ummm, more than six meaningful airports
I have just thought of another airport that serves London. This is Southend which is probably closer to the centre of London than either Stansted or Luton. At the moment the only scheduled flights are to the Channel Islands but in the past there were flights to Ostend in Belgium. Does that count?
I checked Southend, and no, I don’t think past history should count (otherwise we’d be including Croydon Airport ). It does look like they’re trying to expand, though, so I wouldn’t be surprised if a budget service starts up there.
There are serious problems at Southend. The airport wants to extend the runway to encourage more flights but this entails demolishing a medieval church. So you can imagine the objections that is generating.
I’ve heard that about Southend before, but I don’t really understand how it prevents it developing short haul traffic - it can take 757s, which is bigger than almost any passenger aircraft that operates from Stansted. 
Further to the above . Of all the bad luck. This church is probably the only decent building in the whole of the wasteland that is Southend and it has to be at the end of the sodding runway. You just can’t win