[zipper]

Presuming a normal airliner at normal altitude of 30,000+ feet, and one well below trying to follow it, there is an immediate problem. The lower a/c will have a much lower airspeed and be MUCH less fuel efficient

It wouldn't be that far below. The closer the better -- I'm thinking below and behind, 100-200 feet.

These guys weren't likely trained for it, but C-5's fly close formation for 25 minutes or more at a time while refueling from a tanker, with only a few feet separation. 100 feet is much easier.

[C210N]

100 to 200 feet at night? barely less than a wingspan?

dicey enough during the day.

well, it’s a theory!