yo!
We went w/Jet Blue from NY; and took the car seat (for grand son); here is JB's info on it;
http://help.jetblue.com/SRVS/CGI-BIN...ase=obj(373795)
"... checking a child safety seat, it will not count as one of your checked bags and there is no fee assessed..." read more in da Link

Also used seat when in restaurants!

Have a nice trip!