I recall a transcon A319 from IAD last year that had a standby list of 130 due to irrops. I tried to standby for the earlier 777, but that also had a list of 150+, and there was no way I would get on it with all the disserviced pax. No one cleared the battlefield upgrades, since F was already full with people from the earlier, cancelled flights. Fortunately, I used a CR1 or miles to confirm my u/g in advance, so I was lucky.