As you described, that would be the best way to do it. Also @AJ wrote similar while ago, and if you're flying, send planes in the air, before you will go to next level. Small bonus with that fuelI've been saving my Collections for months. I have over 300,000 experience, so I assume I can get to Level 60 quickly. (After making my finger sore 'collecting' each one).
Any tips on how best to advance my levels? I believe each level you advance you get full fuel, so I should make sure I'm close to 0 fuel when advancing...any other tips?