Obviously - a loss is a loss but in this case, it's relatively minor. As someone has said above - with 4 carriers on the route - the market has spoken. AA were just not good enough in terms of quality and reliability and most regular flyers would understand that. AA would be my 4th choice out of 4 to fly MAN-JFK.
Another observation from the comments above: everybody is talking in terms of TCX's presence on the market. What about Virgin's new daily?
As any J Class regular will tell you, the VS J cabin knocks spots off the AA one, especially the (frankly unacceptable) 757 one.
The only people who will bemoan this news are OneWorld status members.
There are still 3 other carriers on the route