I am trying to make a reservation on ual.com. I cannot choose the flights that fits my schedule (leaves after 6pm, direct flights) because the website says, "the selected flights do not have the requested number of selected seats available in the specified service class. please revise your entry." However, from the seat map, the flights look pretty empty. The "availability" from the flight info was indeed 0 in all classes for these two flights. These flights are almost a month away, can they be all sold out?