CO never changes their long haul Int'l number. I think the
LGW numbers have been the same since the 80s. Some like CO34/35 used to be
DEN-
LGW, and was moved to
IAH, but retained the number.
One that was changed was GUM-
MNL which was CO911/912 prior to 2001
I believe
UA still uses PA numbers which I am sure beats the above.
On a sidenote this summer
CO has more than run out of two digit numbers, with a host of Europeans flights seeing 10"X" numbers. Also note
CO 52/53
IAH-
EWR, I can only think this will be the first leg of
IAH-
EWR-LOS at some point?