Tried Air Patrol again and noticed that there is some fuel regen system. Not sure how it works but I would suggest to make it that way. If you have 4 bases - you get 1 fuel every second. If you have 3 bases - you get 1 fuel every two seconds. And so on. It would stimulate player to defend bases and also would let to die from fuel absence not that often (for now it's the most common ending in my Air Patrol runs).
Viewing post in Hornet Virus : Steel Alcimus II comments
Oh really? In this case player can also get additional fuel depending on what target he destroyed (like 1 for trooper, 5 for submarine or so). I also suggest just to stop rotor in case if fuel is absent but helicopter is on a ground. It looks kinda strange that it blows up in this case. Not that it means a lot but it would look like more logical.