There is some generalized situation going on at DEN. Friend of mine was stuck there overnight with Frontier on alleged weather problems and got on his way with UA to AUS.

As far as what crews are responsible, all the RJs from DEN are pmUA crews running CRJs. Not sure whether this is a reflection to the newly ratified CBA with the (merged) UA pilots that allows mainline pilots to fly planes previously classified as RJs or what, but it will be interesting to see how it plays out