Yeah, it probably actually wouldn't be that hard. Just find a section of code that's like "if you are standing on the ground, then recharge booster" and change it to "if flag xxxx is set, then recharge booster" and then just say <FL+xxxx<WAI0001<FL-xxxx to recharge, and then just increase the fuel by a lot like wistil said. The hard part would be making it possible for the player to see how much fuel they have left.