I want to go from YOW to MCO on May 31, and return on June 2, 2009.

According to the Sabre Dot/Res function, the cheapest return fare is CAN$278 ( base fare, pre-taxes/fees). I want to go on either AC or UA - but the web sites' cheapest economy fares are considerably more than that.

Do the fare tools give all published fares, whether they are sold out or not, or only the available published fares? Or to put it another way, why don't I find the chapest bases fares on the AC or UA web sites to more or less match what the KVS tools lists, under it fare functionalities?