I wouldn't fly with the Frontier. It's big and bulky and heavy. It's an expensive seat, not one I'd want to risk dropping and having to replace.
At 2 years and 30lbs her child can easily fit into a Cosco Scenera. Right now you can get one at
Walmart for $39.
http://www.walmart.com/ip/Cosco-Scenera-5-Point-Convertible-Car-Seat-Black-Santee/13004563
It will fit her child just fine, it's easy to install, lightweight to carry. If it gets damaged, no big deal it was only $39.
Have their Frontier moved with the military so that it will be replaced if lost or damaged.