First minor case: the jetpack is lacking a fuel indicator. And I don't mean the "current" fuel gauge. I mean an indicator showing how many units of fuel are remaining in the inventory. It's easy to forget yourself and end up in the air with no charge left.
Secondly - shouldn't the jetpack recharge always when not in use? As it is, the mere act of jumping without activating the jets will prevent fuel recharge (EDIT: walking up / down ladders will prevent this too). The jetpack should always "recharge" when not in use OR it should provide a passive jump height boost and fall-prevention. Or, if that's too OP, then could normal jumps (as opposed to the act of "falling" after flying) simply not interrupt the recharge?