As suspected, Ace Combat Infinity is only for PS3 and is free to play. Will Xbox ever get a look-in? Doesn't sound like it; Namco Bandai responded saying the game was exclusive to PS3.
A new trailer gives a fuller look at the flying game. It's set in the near future, which allows for things like giant flying super-carriers, and has a novel-sounding multiplayer mode. In it, two teams cooperate to attack a common enemy but also compete to inflict the most damage.
No word on what you'll pay for in the game, but buying new planes is probably a safe bet.
Ace Combat Infinity is due out "later in 2013".