Take LIRR out of Penn Station to Jamiaca to catch the the air tran, a LIRR train leaves around 455AM which would get you to JFK easily by 6AM ($5 for LIRR and $5 for airtran). Since you are 55 and 10th will need to either sclep over to 50th and 8th for the C or E downtown (trains before 5AM only run about every 30 minutes) or cab it to Penn Station.