1) The 777 is more diverse and efficient. It generally offers a greater range with a higher MTOW, and customers have a greater "choice" of options (in terms of power plant/range). In this class (250-300 seats), the 2 engine 777 is more efficient than the 4 engine A340. Remember, Airbus went on a smear campaign at the launch of these two aircraft in the early 90s, claiming that four engines were better than two. It was a bit of a PR
2) The 767 and A330 are the most popular aircraft flying Trans-Atlantic flights. With the exception of West Coast-Europe flights (UA and AA
only operate these). Most TATLs can be adequetly served with the 767/A330 range.
3) With the exception of US, the American majors (CO, DL
) are loyal Boeing customers, and naturally went for the 777. UA
was the launch customer, and was one of the big developers/contributers to the 777 project. NW
, only recently retired the DC-10, replacing it with the A330. They don't have anything in between the 330 and 744.
4) I dont' see any A340 orders in the future (in the US). The 777 really killed any potential for the program to take-off in America, and continues to sell.
[Edited 2007-10-10 22:46:05]