C.E.
Check FAA.gov for tips on getting through security at the airport with children (and whatever the current guidelines are for transporting food, etc.) I had a horrible time renting a car seat from a car rental place (I think it was Budget) in New Hampshire when I took my son up there to see his great grandmother when he was 10 months old. I recommend taking your own. The reservation person who took the request for the seat wasn't on the premises and I wound up with a rear facing bucket that wouldn't adjust and wouldn't sit on the seat properly. It was the cheapest, flimsiest possible Cosco car seat and wasn't installed when I got to the car. My son was terribly uncomfortable pitched forward towards the rear seat, and who knows what would have happened if I'd had an accident. It would have compacted his legs. Just take a deep breath and hope that fellow travelers extend kindness to you and your daughter while you're on your trip.