I have been tracking IAH-DCA flights in the evening - which used to be always booked. These flights are now going out many times with empty F seats.

For today, 7/8/08, IAH-DCA (this is a Tueday):
Flight 1558: 9/12 occupied, 3 empty
Flight 658: 4/12 booked, and only 4 on the standby list - likely will have 4 empty.
When 658 is a 738 - then I see even more empties.

Maybe gov't contracts changed and are no longer Y.