Originally posted by Decker
I believe this depends on whether the flights are on the same PNR. If they're not you'll have to collect the luggage and they normally recommend AT LEAST 2 hours for this.
FWIW when I connected UA to BA a while back I had no problems through checking luggage despite being on separate PNRs. I just showed the girl at check-in my BA itinerary and they sent it on its way. When I got to IAD I got my BP from the BA lounge where I was asked to show the luggage recipts and it was all taken care of.
To boot when we arrived at LHR off the BA flight my bag was already on the belt when I reached the reclaim area...and we hadn't arrived on a remote stand [:0][y]
If you have a 90min connection at IAD you might even make it if you do have to go landside and re-checkin with VS. The new 'Premium Passenger' line beside the BA check-in desks is a total breeze and anyone with any shiny card or premium ticket can access it. Even during IAD peak hours I've breezed right to the front of the line [:0][y]. Of course it depends on your UA flight and luggage arriving on time and VS UC line being short. Personally I'd rather just add a bit of a cushion and relax in the Clubhouse [y]