My first thought on refuling rules were this... understanding there would be no real way to make it historically accurate and not wanting it to be a game of refuling. I imagined two landing fields that are not so far apart to be bombed but far enough apart that you could only run a direct bomb route and back without running out of fuel. Any combat or evasive manuvers during this route would result in not being able to bomb the enemys airfield and return safely. As far as why you would go back to the airfield for fuel would just make the game a bit longer, by adding other items of interest without being overbearing and turning into a pen and paper game (where on the table do you have room for that anyway) it would play out like this...1 turn on the ground re fuels, 2 turns on the ground repairs the plane, 3 turns on the ground pilot first aid. You could add more to it but by keeping it that simple you could throw in other simple twist to the game...like re fueling with the enemys gas or taking their bomb stash.