Okay, what do you mean by fly "
1.8 nm apart"???
The article says:
n tests, two planes used the Formation Flight Information System to fly 55ft apart over the same distance. Initial results suggest the trailing plane used 12 per cent less fuel than the lead plane.
I suspect they'd have to fly very close together for maximum fuel savings.
Look at how closely race cars and cyclist follow each others tails to benefit from drafting.
Geese coordinate the way that they flap their wings to maximize the benefits of each others slipstreams. I doubt that planes or helicopters could gain advantage from such subtleties unless they pay close attention to wingtip vortices.
Don't forget the V formation in flight. It helps geese even if they only have one goose to one side of the lead goose, with the rest of the flock angling off to the other side.