The main problem - it is far more probable that you run out of fuel, than that you crash into a bird or fall off the screen. Either make the fuel go down at a slower rate or make sure that the fuel power-ups appear regularly. Maybe the best solution is to make them refill your fuel completely.
The game would overall be more attractive if you added another danger (e.g. storm cloud/mountain, which must be flew round), just a new factor which can't be met directly at the start.
Then, the cursor is doubled (at least for me) and you should have an option to return to the main menu, not just to Retry game and Upload score.
Aside from that, it's a funny game with neat graphics.