Have a great time in the Big Apple! Try to bring some treats and maybe a chew toy for the flight, along with a shirt or something in the carrier with your scent on it so he feels right at home. Let Sully potty right before going onto the plane if possible or bring a pee pad and take him to the lavatory if he needs to go during.
Although technically you're not supposed to hold him during the flight, I've been told that if the flight attendants aren't looking, or aren't overly mean, that you can get away with it and let him lay on you during the flight... (just cover him with a blanket or something) if someone walks by. We all know how well Mr. Sully is trained!