I've install two fuel tanks, refuel ship (160/160). When trying to send ship to UFO, I get:
I didn't really understood if the problem is when you try to go to a mission (with battlescape), or when you try to intercept a flying UFO.
Could you also confirm me that you are using a Firebird ?
And that would be nice if you could do 2 other tests for me, please:
1. after you got the error message, enter the console and type 'debug_aircraftlist'
there is a rather long output, could you give me the lines begining with 'stats' and 'fuel', please (for the firebird if this is the aircraft you use). It should look like:
...stats: 0 7 0 0 0 0 160000 0
...fuel 160000
2. Could you see if the is a savegame problem by starting a new game (I guess you're loading a savegame at the moment), and see if this bug still exists.
Thank you