Silverpie is absolutely correct. When operational problems occur (weather, mechanical), all rules are waived. I was referring to a situation where the passenger initiates an optional request for personal reasons.

One thing I have noticed, however. Gate personnel will often let you fly into a nearby co-terminal. For example, in DC if you buy a ticket to/from BWI or IAD to save money, the gate agents will often let you standby for the flight to DCA, especially if it is an off-peak time.