m60, if your fare says no standbys, it means just that. If your ticketed flight is oversold, that would be a different story, as flying on an earlier flight would help the situation. But if there are plenty of seats on your ticketed flight, why should US break the rules just for you? Presumably you paid less for the ticket in exchange for no standby. If you want a fare with standby allowed, pay more. The fact that it was on a Sunday is irrelevant.