· No. This is something the airlines strongly discourage as they would be unable to forecast loads and yields if they were to operate this way. It would result in anarchy and riots at check in counters.

You can of course turn up and go if seats are available but you will usually end up paying the highest fare, not the lowest. A separate issue is standby fares given to those who work in the airline industry as a concession. These are not generally available to the public.
Mike Preston