Restart from Checkpoint Trick

There are long missions that requires you to destroy a lot of targets with no return line to repair and re-arm. In these missions, as long as you reach the "cutscene checkpoint", you can safely restart from checkpoint deliberately with your plane fully repaired, and ammo fully replenished - without affecting your score.

The only downside to this trick is that an enemy ace might not appear after restarting the checkpoint if his/her spawn conditions are in the pre-checkpoint part of the mission. However, on normal circumstances, this is a very effective trick especially when you're trying the Machine Gun Maniac campaign run or simply trying out the harder difficulties.