All the seats on one leg of our PVD>DFW>DAL>PVD flight are greyed out and no changes are possible currently. Suspect this is due to a schedule change, they did mention there is a change being made to one of the flights when I called in to change my departure time. Is that what normally what causes this? If so, any idea how long typically does this take to propagate through their booking system and open those seats back up?