Yes, it's doable. At 14:00 it should be before the traffic so a taxi ride into town will cost about $50-60 and take about 40 minutes. The Airtrain/Subway http://www.panynj.gov/airports/jfk-to-from.html takes a little over an hour and costs about $8 per person including the subway ticket and the Airtrain ticket. Take the Airtrain to Jamaica and then get on the "E" subway line. Get off at "7th Avenue" and you can walk to Times Square in 5 minutes. Coming back to the airport, I'd suggest the train as you'll want to be back at the airport around 1900 and you'll otherwise get stuck in traffic if you leave town at 1800. (Not sure if they still have the helicopter service from the East 30th street heliport). If you stick to Midtown Manhattan, there's a lot you can see at that hour and mostly on foot. You'll have 3 hours in town so you can go to the "Top of the Rock" at Rockefeller center for a view of the city. Have a corned beef or pastrami sandwich at the Carnegie Deli on 7th Avenue. Walk around Central Park, go to the Museum of Modern Art, Times Square, etc.