Linda, Pegasus are similar to KTHY on seat prices , ex amount of promo / next cheapest and super prices , once the cheapest are sold out then they quote the next price and so on till they are all sold out, then it will show as sold or no flights.
EG cheapest Pegasus from gat to dal on 7th june gone up to £164 from £114 yesterday
it pays to snap them up quick for the deals.
contact me via my profile if i can help re flight deals comming up on my data base.
Ron