Most code shared flight.....
 

Sitting here at SK lounge in SIN and looking at the departures list there is a flight SIN-KUL which is code shared by SQ (+ presumably all other *A carriers), MH, AA, VA, MI, WY - talk about over-code-shared and a varied mix......wonder what the most code-shared flight in the world is.....?

I wonder if there are US Airways flights that are code shared by both AA/One World and Star Alliance partners in the run-up to the AA integration and full withdrawal from *A, which I believe happens in March.

Such cross-alliance codesharing is not all that uncommon. Lots of bilateral agreements exist outside of the alliances. Copa puts its code on the KLM PTY-AMS flight even though they're in different alliances.

Doing research I found Etihad flights between SYD/MEL & AUH have 14 codeshares. (The most I could find for other airlines, including the routes served by US Airways/American, were from 9 to 11 codeshares.)

For example, EY 454 AUH to SYD:
(S7) S7 Airlines 4605
(HM) Air Seychelles 5102
(NZ) Air New Zealand 4254
(B2) Belavia 354
(EI) Aer Lingus 8054
(ME) Middle East Airlines 6636
(KL) KLM 3938
(OA) Olympic Air 8054
(VA) Virgin Australia International 7454
(AF) Air France 3820
(AZ) Alitalia 3928
(JU) Jat Airways 8582
(KQ) Kenya Airways 5502
(AB) airberlin 4070

It seems that Ethiad, which is not a member of any of the global air alliances, has been looking to feed traffic to its Abu Dhabi hub through its strategic codeshare partnerships and equity stakes in several airlines. The airline has more than 40 codeshare partners, including JetBlue as the most recent. Additionally, the airline will build a U.S. Customs Preclearance facility in Abu Dhabi.

Air New Zealand and TAP Portugal also had many flights with 10+ codeshares. For NZ this is probably because of its remote location. Rather interesting finds.

United have dropped all of their code-share flights with US, although I'm not sure if other *A carried have done the same yet. Multiple people with reservations that were on the UA codeshare flight number have reported them changing to the actual US number in the reservations, although I'm not sure if that's for all flights, or just those beyond March.