I've had no problems with a BD*G Card on United flights accessing the RCC's.

You should have no problem with US Airways (although they might be confused who BMI are )

As stated, if you're a UA*G or US*G, you have to pay for club membership - Especially for those lovely crackers, shortbread, packed cheese and Sunchips (that's the IAD C7 lounge experience )

Of course if you're at an Oceanic gateway on the way over an ocean, remember to claim your drink chits as you go through