Flying GUM-SPN r/t next month, the fares there seem to be priced by flight#. (EG. N-class is $85 one-way but only for the 2:45 AM GUM-SPN flight, other flights are $100 or $147).

Can you standby for a later/earlier flight, if the fare class is available? Or will standby have to follow the same fare/flight# rules?