Fuel contracts come in three varieties you will unlock through the game: Instant, Flexible, Take, or Pay. Instant contracts are the most expensive but are the fastest. Once you sign one a truck is immediately dispatched. It’s a great “get out of jail free” card when you run out of fuel at any point in the game but is inefficient to use over the long run. Flexible and Take or Pay contracts are very similar. These allow you to schedule a fuel delivery for a certain time. We would recommend setting up these deliveries to be midway through each wave of aircraft on your schedule every day. The order of precedence is usually unloading passengers and bags, after flight inspection, loading food, then fueling, so expect to see your fuel levels drop in large chunks at certain intervals. The only downside to these contracts is if you order more fuel then you have the capacity you still pay the same rate. Adding tanks, later on, will alleviate this as they are cheap and give you tons of room.