Take the E or F train to Roosevelt Ave./Jackson Heights (also a stop on the 7, G, R, and V), then grab one of the black livery cabs idling on the street. Pay $12, spend 8 minutes on the expressway, and you’re there. Total time from Rock Center: 30 minutes. During rush hour, this route will save you at least half an hour.
The AirTrain is the surest way to get to JFK. First you have to get to Jamaica—which is easy enough if you jump on the LIRR at Penn Station or Atlantic Avenue (20 minutes). (The E and J trains will also get you there, but the subway is much slower than the LIRR.) From Jamaica, the AirTrain’s loop route can have you at the gate in as little as 5 minutes, depending on your gate. The closest gates are at Terminals 1 (international carriers) or 8 (American). But even a trip to the farthest stop—Terminals 5 and 6, home of JetBlue—takes no more than 20 minutes.
Newark’s airport transit isn’t as efficient as JFK’s, and the connections can be inefficient, so if it’s not rush hour, you might consider taking the 1/9 subway to Canal St. or the C/E to Spring St., then forking over $49 for a cab right by the Holland Tunnel. But if you’re facing traffic—especially the evening rush—take New Jersey Transit from Penn Station to the Newark Liberty International Airport stop (about 20 minutes), then transfer to the AirTrain to get to your gate (another 15 minutes). Depending on wait times, the whole trip can take an hour, or even more, but at about $20, it costs less than half what a cab or car service would charge.
The fastest nonpublic transportation: US Helicopter. But it’s really only worth it to drop $149 on a helicopter ride to the airport if you happen to be down by Wall St.’s harbor or near the company’s E. 34th St. heliport—and you’re flying Delta out of JFK or Continental out of Newark. (Security clears you before you board the helicopter if you’re flying on these carriers; for any other airline, you’ll have to take the airport monorail to your gate and go through security there, effectively losing any time you saved.) Flights leave roughly every hour in the business day from Wall St. and in the afternoons from Kips Bay and take only 10 minutes. You can leave the helipad as late as 6 p.m. and still make a 7 p.m. flight.