USAir and AA are alliance partners, although I don't think you can transfer miles. What you can do is when you ask for your reward ticket (on either airline), you can mention the fact that you have available mileage on the other's FF account and then "pool" the mileage for the award ticket.

That is, I believe, the agreement between USAir and AA.

EMD: Why did you choose AA as the other airline to consolidate your "other" mileage?

I'm in the same position and I'm choosing American due to it's fares to the airports I fly to plus their service in the Carribean and Central America. I could go either Delta or USAir or United... it was a tough choice considering everything. I decided against Northwest due to all of the problems I seem to have each time I fly them, and I decided against Continental only because they're Northwest's partner airline.

If you are going to fly American more, did you see the thread under American Airlines regarding the "The Elite Challenge"? That appears to be a quick way to get to an AA elite status.