Needs some tweaking
A few problems.
For one, in the early stages, you sometimes have waves of aircraft in your view, then about 10 seconds will go by that there are no aircraft at all.
Also, if you get a large combo that will beat a level, the points should be awarded immediately. you shouldn't have to wait for the bar to climb up because you just scored 3000 points in one combo, and run out of gas in the process. that is seriously lame.
Other than that, decent game to play if you have 5-15 minutes you want to kill