If there's a list of best PSP games, this game should be in it. While not made by Project Aces, (Access Games made this one. The same devs who did Drakengard 3) the quality comes exceptionally close to the PS2 titles despite being a handheld title. I guess it being a PSP is its biggest fault. The story is fine with accompanying artwork albeit less noteworthy, gameplay is the same as 5 which is great although they also reintroduced branching missions, added more fictional aircraft (some from previous games) and introduced aircraft customization and that gives it tons of replayability. It gives a good challenge and a satisfying payoff with its mission variety (though some levels might be BS too especially the gas mission). The soundtrack is a banger as always even though the sound team is entirely different from the previous games (one of the people from the sound team is the composer of the Index anime series). It's also probably best experienced on emulator as there are enhancements and finding a legitimate copy is going to be tough as you can only get this on UMD and this got removed digitally years ago. If you own a modded PSP though, that will also do. The controls on the smaller analog is still pretty good and playing it on the go is still worth it.

I highly recommend this game. Whether you are a fan of the series or a newcomer, don't skip it. It is a gem that I hope more people discover.