The game looks awesome, the planes looks amazing and work well with the sound effects and music.
I did find it a bit difficult, I also noticed that enemies were able to destroy each other and this gives points to the player (don't know if this was intended).
Nice use of font for the game over screen, it really screams that something bad had happened.
When moving forwards it seems that you destroyed some of your own bullets (this however didn't damage the player so I can't see it as a massive issue).