Into SFO (fog delays), this has not been the case for me. Luckily, last night, my 737 () ORD-SFO got in early while others were delayed.

I've taken 763s/762s from JFK-SFO before only to be delayed significantly because of weather. However, it does seem like short-haul, narrowbody flights are given a lower priority by the airline (See LAX-SFO ontime statistics for more info on that!)

Perhaps because AA has virtually no connecting passengers going through SFO, or a very minimal amount on any given day, its an exception to their rule.