Originally Posted by
Jeremy3292
Thanks everyone. I guess I'll just have to find out upon arrival at the terminal to be sure! Is it likely UA and BA will be in separate terminals at IAD? This would increase the hassle and time needed between flights obviously.
There are no separate terminals at IAD. All gates are on the sterile side of a single set of checkpoints and all check-in counters are within relatively easy walking distance of each other. If by some chance, UA checks your bags through, then you will simply head from your arrival gate to Concourse B via walk, AeroTrain or moon buggy as the case may be. If your bag is not checked through as I suspect it will not be, then you will need to head to baggage claim, grab your bag and schlep it upstairs to AA/BA check in which is further than UA check-in, but not appreciably so.
BTW - Your TA's answer makes zero sense. UA has had interline ticketing agreements with both BA & AA for 50+ years.