The whole business with snow and airports reminds me of a comment of W.S. Gilbert.
'Although Saturdays come round with amazing regularity, they still seem to catch the Metropolitan Railway by surprise'.
The same for both BA and BAA.
In BA's case, it's the crap back office staff that let it down -plus stupid rules. It proved cheaper for me to cancel a ticket and lose the original fare and buy a new one in a higher class than to take the upgrade they offered.