Although it is possible that I am reading too much into this matter, it seems like American Airlines might be looking to add flights to Mumbai in not too distant future.
American Airlines expands to India
American Airlines has suffered in several major international markets, where United Airlines has experienced significant growth. This is changing.
It is great to see American expanding service in these markets. American will partner with IndiGo, India's largest airline by passenger carried. Although IndiGo is a low-cost carrier, it will offer passengers many connection options.
American adds flights to India and Israel
American will codeshare from Mumbai with IndiGo
American and IndiGo applied to the Department of Transportation (DOT), Tuesday, in order to obtain approval for their codeshare agreement.
As @IshrionA noted, there is something very interesting about the filing. American originally planned to codeshare with IndiGo on 29 routes in India from Bangalore and Delhi. But that number has drastically increased. According to the filing, American plans to codeshare with IndiGo for around 100 routes out of Mumbai, Delhi, and Bangalore. Below is a complete list of codeshare routes.
What should we make of the codeshare agreement out of Mumbai? If American does not fly to Mumbai, then there will be no need to codeshare with IndiGo for point-to-point routes from there. Here are some thoughts:
It is not uncommon for airlines to ask for more permission than they really need. This gives them more flexibility.
This suggests to me that American may be considering adding service from Mumbai in the near future
It seems more likely that there will be a new route to Mumbai; American appears to be taking a fast-growth approach with new long-haul markets (just take a look at how American has added three routes to Israel in such a short time), and I believe India will follow suit.
American should launch flights to Mumbai from New York or Seattle. The flights are nearly identical distances (7.800 miles) and American could leverage its partnerships to JetBlue and Alaska.
I want to emphasize again that nothing is concrete at the moment, but only clues. It would be shocking if American does not announce a route from Mumbai in the next few months.
American and IndiGo have a codeshare arrangement in place
Bottom line
American Airlines plans to soon launch flights to India. American has also established a codeshare agreement for connectivity to Indian gateways through IndiGo. According to the DOT filing, IndiGo and American are planning a codeshare agreement from Mumbai. This suggests that American might launch service to Mumbai in not too distant future.
This is a very likely scenario, and I would guess that a route to Mumbai could be found from either New York City or Seattle.
Are you positive that American Airlines will offer flights to Mumbai?