There's no easy one-size-fits-all answer as far *where* the airplanes go, but it's better if you know the overall process.
I'm an aircraft dispatcher, and I work for a major carrier here in the USA. By FAA regs, all airlines must have dispatchers, and one of the many things we do is plan flights, monitor their progress enroute (but not separate them--that's ATC), and take action(s) when thing change that will prevent the aircraft from landing. Most of the time, this last item comes up unexpectedly, like when unforecast fog or thunderstorms pop up. With Floyd, we could see where/when we were going to have problems in advance, mostly with the storm's winds, and the resultant crosswind situation at a particular airport. Since there are maximum crosswind limitations that must be complied with, we couldn't operate until the winds abated.
Depending upon when an airport was forecast to be unavailable to us, we modified flight routings. For example, if the aircraft was scheduled to operate into RDU and then spend the night, we canceled the passenger flight into RDU, and then ferried the aircraft (empty) to the airport that would have been the first stop from RDU-??? the next morning. That way, the aircraft starts out, on-time- in ??? and flies the remainder of the day on-time.
Believe me, with Floyd, we've been *BUSY*
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.