Slightly OT, but a former coworker of mine flew gliders as a hobby. Like an ultralight airplane without an engine, they get towed up to 10000 sq ft and then glide.
Guess how long they can stay in the air? Hours. Gliders stay afloat by finding hot air streams where clouds are forming, riding the plume up, then gliding to the next cloud.
It's not what this RC plane was doing, obviously, but posting it as an example showing how fuel can be irrelevant in the air. It's also an amazing hobby for one to have. He has all sorts of stories about the weather changing and having to crash in a farmer's field...
My father and stepbrother used to do this as well. Lots of interesting stories came out of it - having a heart-attack five thousand feet up, landing in a farmer's field and convincing him to put down the shotgun...
Guess how long they can stay in the air? Hours. Gliders stay afloat by finding hot air streams where clouds are forming, riding the plume up, then gliding to the next cloud.
It's not what this RC plane was doing, obviously, but posting it as an example showing how fuel can be irrelevant in the air. It's also an amazing hobby for one to have. He has all sorts of stories about the weather changing and having to crash in a farmer's field...