It's a neat concept, and you should be happy about that, but at some point, it gets hard to keep track of what you have and how many you have. Also, I don't really see the point of the engine failures if they don't cause a lose state, just a small wait. Seems more of an inconvenience to the player than anything in-game.
I like the pacing of the game, though. It's just right, minus the engine failures. Good submission!