I was wondering what the shortest current flight in the UA system is, for both mainline and express?

I think that IAD-LGA may be the shortest mainline, but I feel like there must be shorter mainline originating from ORD.

I'm pretty sure that the absolute shortest UAX may be AOO-JST (or whichever way it runs) on a Colgan Saab, but what other really short routes are there? PDX-SEA and LAX-SAN are pretty short too.

I checked out this thread, but it seems to have all flights that don't exist any more such as IAD-BWI and SFO-SJC, so I was wondering what the current shortest are.