IIRC, US is not participating in the *A upgrade program. Also you can buy somthing called "PT500" upgrades (I think they work like UA's e-500's), but you must be premier or higher and around North America (no TATL).
Here are the t & c's:
Validity: For use by Mileage Plus® members when traveling on United code-share flights numbers 6000-7499 (UA* flights that are operated by US Airways®
, as well as regular US Airways-operated flights. Each PT500 upgrade is valid for up to 500 miles of travel. A minimum of one upgrade is collected per flight segment.
Travel Area: Published routes within/between theUS, Canada, Caribbean, Mexico, Central America
Carriers: US Airways and US Airways Shuttle®
Valid Fares: Based on Mileage Plus membership level - Premier®, Premier Executive® and Premier Executive 1K® members may use PT500 upgrades with the purchase of Y, B, U, M, H, K, Q, V or L fare classes. General Mileage Plus members may upgrade with the purchase of Y, B or U fare classes. All rules of the purchased fare apply.
How to Purchase: PT500 upgrades may be purchased anytime in advance or on the day of departure at US Airways airport ticket counters, US Airways Clubs or city ticket offices. They cannot be purchased at the gate. Paper certificates will be used and they are personalized.
Pricing: Mileage Plus Premier, Premier Executive and Premier Executive 1K members may purchase PT500 upgrades for $40.00 each. General Mileage Plus members may purchase them for $50.00 each.
How To Request: Upgraded seats may be requested upon check-in on the day of departure only. Advance reservations will not be accepted.
Upgrade Processing: By elite level, then time of check-in.
Expiration: 1-year from date of issuance.
Transferable: Customers may transfer PT500 upgrades to one companion traveling with them
Mileage Value: PT500 upgrades cannot be exchanged for Mileage Plus or Dividend Miles. Frequent flyer miles are earned based on fare purchased when traveling in an upgraded class of service.
Flight Interruption: In the event of a flight interruption, alternate travel is only provided in the class of service purchased.
Other: These upgrades cannot be deposited into a Dividend Miles or Mileage Plus upgrade bank.