I phoned United today trying to change a flight out of DCA (9/19) via IAH to LBB to one going a different route.
But the flight I wanted (from IAD via DEN) only had one seat and I needed two.
I asked the customer rep. the status of flights today, and she said all the flights so far from DCA to IAH had been on time, and one flight from IAH to LBB had been delayed.
So, for now I'm staying with my original schedule, with fingers crossed...