Lots of good ideas killed by bone-headed mission design.
And what does the developer does with all that? They wrap up all that good stuff into some tremendously annoying missions. You have to fight huge waves of enemies, mostly by yourself. One after another. Shoot down 20 Stukas. Then shoot down 30 Messerschmitts. Then 30 more. It makes me feel like playing a late 90s MMO. What am I grinding for? Shooting down 1 Stuka is fun, 2 is cool, 4 makes me feel like an ace, but why do I have to do the same thing 20 times in a row?
Most annoyingly, there's no in-mission save. At all. When I shoot down the first huge wave, the second, and then the third, and then the next 30 enemies strolls in, there's no more fun, no more challenge, just a boring chore to complete the mission because if you quit, you'll have to redo all the waves all over again.
Video games are all about mastering simple repeated tasks, but something went wrong with this one. You can only do turn-hold-acekill so many times before the game loses all appeal. I'd have loved this game to have fewer, more challenging enemies, more varied objectives, instead of basing all gameplay on forcing me to shoot down huge formations of the enemy single-handedly over and over and over and over and over again.