Originally Posted by
jb008
Thanks for the Flightaware suggestion!
I tweeted DLAssist for this specific flight in question and it turns out that the plane is there, but the crew is late due to a weather delay. That might be why I couldn't find a link about where the incoming plane was coming from.
Flightaware doesn't have the info because DL4920 is operated by ExpressJet. The way Flightaware tracks the inbound flight is by following a tail number, which DL and most of its regional carriers provide to Flightaware (or some data source Flightaware has access to); however, for whatever reason, ExpressJet does not provide tail numbers to Flightaware and thus the inbound cannot be tracked there.
However, one nice thing about ExpressJet on most routes other than ones that begin or end in ATL is that they only operate a handful of flights that don't transit through ATL. So in a case like this, I like to go to flightstats.com and search by airport arrivals. Under carrier, enter ExpressJet (NOT Delta!) and you should be able to figure out where your plane is coming from pretty quickly as there just aren't that many ExpressJet flights out of DTW.