This wasn't very well publicized and sounds like it's being done under the cover of darkness... but in case you are wondering why you are seeing US Airways signs in Terminal 8, this is the reason:
US Airways to Move to American’s Terminal 8 at JFK
US Airways, which is planning to merge with rival American Airlines later this year, will move to American’s Terminal 8 at New York’s John F. Kennedy International Airport on Wednesday. The airline operates a relatively small number of flights out of JFK, eight on average, mainly to its hubs in Charlotte and Phoenix...