I praised Kayak's flight selection service a few posts back, but I'm finding they are listing flights that are not available even after what appear to be many hours of non-availability. However, this does appear to be an American Airlines data problem more than a Kayak one so I'm still bullish on Kayak, but it sure is frustrating to see this note which appears at AA.com:

Check below for errors:

• The flight you selected is no longer available. Please select another flight or modify your request

Arrgghhhhh!

A detailed study of the many services really is needed. Maybe I'll put that on the list.

UPDATE:  Using Kayak.com which sent me into AA.com booking system I did get an excellent rate MFR to BWI of $384 which appeared cheaper thanat AA.com's rate when I searched there independently of Kayak.  The 384 was over $100 cheaper than Orbitz, Farechase, or TravelNOW.