Thanks guys! Question, this will be our first time using the Islip airport. On our return Sunday I have looked at the train schedule and we really need to be on a particular train. Any chance of sellout? I know thats probably a goofy question, but just want to be sure. Unfortunately, it's the 9:15am (ish) train we need to be on. Anything later will be pushing our transfer time before the flight.

9:15 AM on the LIRR on a Sunday? Don't worry, the train will be empty.

Plus, trains never sell out. There are so many people that have monthly passes that they can't keep track of how full a train will be. On peak hour trains, there are often many people that have to stand.