I just found a bug on mission 4, when the bombers came one of them went out of the mission area and is just continually flying away. I have to restart the entire mission because of this bug. Annoying, but the game is fun enough to play the entire mission again.
If there was a multiplayer game with the same mechanics as this, it would be amazing. However, this game is still a great game, although obtaining the 50 hearts took me a while. 5/5