In my long experience with US Air and Delta Shuttle -- yes with USAir you always have to pay a fee for any change to your itinerary. Im not quite sure I understand your change from USAir to AA? Where are you flying from to? Nonetheless call USAir and ask them -- also be sure to register for 6 times the miles -- just give them your USAir and United FF# and you will receive SEXTUPLE miles. This is why one should fly delta shuttle. It's much preferred to USair's service and they are more flexible with intinerary changes.