I was thinking of this in terms of aerial refueling. It's always better to take off with less than a full tank of fuel. Once you're airborne, the aircraft can

I was thinking of this in terms of aerial refueling. It's always better to take off with less than a full tank of fuel. Once you're airborne, the aircraft can top off its tank to complete its journey. Of course, it may even be more economical to top off at multiple legs as the journey proceeds. To your point, a "reverse" refueling would also be ideal in order to lower the weight of the aircraft. In certain contexts, it's already being done. It'd likely need to be much safer in order for civilian aircraft to carry out aerial refueling though.