Free Standby Now?
#46
Join Date: Jul 2007
Location: San Francisco/Sydney
Programs: UA 1K/MM, Hilton Diamond, Marriott Something, IHG Gold, Hertz PC, Avis PC
Posts: 8,147
Once you're at the airport, or if there's any type of IRROPS, then anything is possible and it doesn't hurt to ask - but the odds of you succeeding are at best very low.
As an example, a few days ago I changed from PHL-IAH-SJC to PHL-SFO over the phone a few hours before flight. Technically that's not allowed, but my PHL-IAH was delayed and my connection was looking unlikely so they were happy to make the change.