OOOO! I hate that bug, A lot of effort went into that boss fight and it sucks that people are missing it. Someone did find a bug to skip to the second level though if your interested.
start the game normally and then hold the fly button down until you get the black screen and keep holding it down. the level will start again but the screen wont scroll but you'll still be able to fly to the end. you'll know it working if you can still see the exhaust passing over the screen after a minute of holding down the Fly button you be at level 2 (there will be a screen transition)