...and decide what to make available?

I ask because I logged in to CO.com trying to figure out my next DC - (MEX or TLC) trip; after checking different days and airports the EWR-MEX routing never came up. Had to do a multiple segment search for it to finally come up in H. But after 20 minutes of searching I lost track of all the options so I started completely over and taking notes.

Lo and Behold, DCA-EWR-MEX comes up on the first new search in T.

Sure, someone could have cancelled, but are they savvy enough to monitor searches and adjust fare buckets accordingly?