Well, I think it is a very interesting idea, and as DaveReid says in #3, geese don't seem to have a problem. (Great comment, Dave
).
However, the logistics will not work for airline travel. It will not be possible to coordinate two or three aircraft to fly at the same time, same route; any fuel saved would be used up by getting into formation in the first place. If it were feasible, the A380 would have done much better.
Might work for freighters.