Just tried to do a TPA - PIT RT for the weekend of Nov 12th returning the 14th. On Friday (12th) I saw 10 or 12 choices. I picked one for the 12th and the system came back and displayed only one choice for the return on Sunday (a 3:11pm going through JFK). I knew that there were more options (going through ATL, DTW, CIN etc) so I played around and changed the option button to search from cabin to fare class and about 10 or 15 flights then showed up on the return. Since both of the cabin options were for economy and there are plenty of seats, seeing only 1 flight on Sunday is a problem. Once I switched from searching back by fare class to cabin and started over searching by cabin, the multiple flights showed up on Sunday...

Just went into Delta.com and had it happen again on a trip from TPA - BWI.