David - it is quite common in the States. USAirways is re-registering
their a/c as they get painted into their new scheme after the merger
with America West.
This a/c is indeed an ex Piedmont, originally N793N.

Ken

I guess they must have the money to spend.
My company (should I say the company I work for) did not bother
to change the registration numbers on any of the planes after either
merger/buyout. For years you could spot a former Western or
Pan Am plane in the fleet by its registration number.
Most of those are gone now, but not forgotten.

David