UA benefits significantly from their AI codeshare.
Not to hijack a thread about AA, but UA and AI don't have codeshare. If they did, AI would be flying double daily flights to EWR and ORD and daily flights to IAD.
Re: AA to India, the safest origin would probably be JFK, the most profitable would probably be DFW and the out-of-the-box origin would be LAX (especially with a codeshare on AS to SJC). On the flip side, JFK yields would be terrible, DFW would be stretching the limits of any aircraft other than 77L and AA is terrible at LAX, not to mention having to compete with CX.
For all the people talking about a potential PHL-India flight, I'd like to point out that no one from the IAD or the EWR/JFK catchment areas would drive all the way to PHL to catch a direct flight to India, especially when UA and AI are competing for their business. I don't have the factfinder.census.gov report handy, so going by Wikipedia's numbers here, PHL area has about 90k people of Indian origin
. Since NA-India flights are still predominantly VFR, that number has to be bolstered significantly by connecting passengers in order to make PHL-India work. QR also siphons away a significant chunk of the addressable market, which makes it so much more harder to sustain a PHL-India non-stop.