Robert M. Gary wrote:

Sam Spade wrote:

Thus, it can only be used in the destination terminal area, after a lot
of arrival dalay holds, delay vectors, etc.


It is probably most often used by oceanic flights after encounting
unexpected winds or having flown at an unexpected altitude. No need to
have "a lot of arrival delays".
Flights don't carry a lot of extra fuel since its very expensive to
haul a bunch of extra fuel up to 30,000+ just to return it to earth and
cargo pays better.

-Robert


My experience was that it is used by transcon flight more, simply
because there are more of them.