> A train could do this in 20 minutes or so.
There’s already a train that does this. It’s the express A train, which gets you to the AirTran. And as someone who has taken the train from Manhattan to JFK on multiple occasions, it most certainly does not take 20 mins or so. It takes at least an hour and that’s not including the highly likely delays.
I think it would be inefficient to have a dedicated train take up the line just for JFK.
Stockholm with a bit over 1 million people has an express train from Arlanda airport to the center of the city, it goes at ~200km/h making the transit of ~40km in 20-25 minutes.
I don't understand why it would be inefficient for one of the busiest airports in the world to one of the largest cities in the world to have a similar setup.
Do you know where JFK is? JFK does not sit outside the city like Arlanda. JFK is in the NYC Queens borough surrounded by highly dense urban sprawl. That setup makes sense for an airport that sits far outside the city.
No track to JFK can support anything near a 200km/hr train and building a track for such a train is a nonstarter.
It'd likely have to go largely underground. This is the approach being taken for Dublin Airport (again, a far, far smaller city than NYC); it'll be served by a largely underground metro line, running every 3 minutes each direction, taking about 20 minutes from the city centre.
Now, the catch there is that this metro isn't going to the airport, it's going _through_ the airport. Even without the airport it would be justifiable, so the airport kind of gets it for free. That's probably the only scenario where you can justify this sort of thing; it would be comically overkill if it was just to serve the airport (it will be able to move 20,000 people per hour per direction, which is... a lot more than the airport can move.)
That said, you'd think something along these lines might be justifiable; as you say, the area surrounding JFK is dense.
the LIRR also goes from manhattan to jamaica, and it does in fact take 20 minutes or so (21 according to google maps)
You can only pick up the LIRR from midtown and the Jamaica endpoint is the AirTrain which requires a separate fare and another 10-12 minutes to get to the terminal. Having said that, AirTrain/LIRR is my preferred route into Manhattan on business travel, but I always take an Uber out to the airport unless I've got a late night flight.
I always counted 50 minutes from midtown to JFK, taking the E train to Jamaica station and the air train.
But I think GP's point is that it could be done in 20 minutes. The A train is a subway, it's nowhere near the speed of the Heathrow Express.