I always thought it represented the order of check-in, as when I
check-in on line 24 hours ahead, I get a very low number, and
when I don't, I don't ... but today, as I had two horses shot out
from under me (at two separate airports), I was put on US3278,
with SEQ 143, so I pointed this out to the concierge at the club;
she said that she didn't know what it meant, but it couldn't possibly
be the check-in order, as there are only 86 seats on the aircraft.
I thought to myself, maybe there were 57 people who checked in
and then unchecked in? Any ideas?