alt Hacker NewsStockholm 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.