That's not a huge amount of time, but it should be doable. Unless, of course, you're delayed coming into Newark, which happens a lot, or you hit traffic in the NYC area, which happens a lot, or the fact that you're arriving during "rush hour" car traffic, or there's a big line at security, which happens a lot. But, cross your fingers a bit and it should be doable.
Hopefully, you won't be waiting on checked bags. Go straight from the CO
airplane to the taxi stand. That'll take about 15 minutes from the door of the airplane. Wait in line for taxi, another 15 minutes. Get in the taxi. It'll now be about 8:15am. You have 3.5 hours.
There are a couple of ways the taxi can go. One is the New Jersey turnpike to the Goethals bridge, across Staten Island to the Belt Parkway, to JFK
. On this route, you'll be going in the opposite direction of commuter traffic on the Turnpike, but *with* the commuter traffic on Staten Island. Once you get to the Belt Parkway, it will be opposite to the commuter traffic, but the Belt is heavy in both directions a lot of the time. It will be at least 8:30 by the time you hit Staten Island, though, so it won't have too terribly long to go until the end of rush hour.
Another possibility would be to take the Turnpike to one of the Hudson River crossings (e.g. Lincoln Tunnel, Holland Tunnel, GW Bridge), go through Manhattan, and across Queens or Brooklyn from that direction. Problem with that is that you'd be going into Manhattan right at peak commuting time and you'd get hung up in Manhattan.
The cab will be very expensive.
An alternative would be to take the Newark Airport monorail to the NJ
transit station on the Northeast Corridor rail line, switch to whatever the first NJ
transit train stops there, go one stop to Penn Station, Manhattran, walk downstairs to the Long Island Rail Road, get on the first train to Jamaica, Queens (all LIRR lines except the Port Washington Line stop at Jamaica), change at Jamaica to the JFK
Airtrain. This should be cheaper than a cab, and not subject to the vicissitudes of traffic, but, let's see how long that would take. 15 minutes from door of plane to monorail, 15 minutes wait for monorail and getting NJ
Transit ticket at monorail station through to Penn Station, 15 minutes to NJ
Transit station, 20 min or less wait for train, 30 minutes on train to Penn Station, 15 minutes to change trains, 20 minutes to Jamaica, 5 minutes to change trains to Airtrain, 20 minutes to terminal. So, that looks like about 145 minutes, or two hours and 25 minutes to do it by train. Of course, with quicker transfers than I have allowed, it could be much faster. There's a thing at www.panynj.com (port authority) on how to take the Airtrain with transfers between the two airports. DON'T take the subway. Dangerous and slow.
This all assumes that you're traveling on a weekday. Weekends will be very different, both with regard to auto traffic and the frequency of rail service.
All the best,