The 767-400 is going to do just fine. We love the 767 at Delta, and there's no reason not to love the -400. It fills the 763/772 gap perfectly, and has a perfect niche within the Delta system, doing the high-density domestic runs and Hawaii trips.
Part of the problem is that you people expect a new aircraft to sell like the 777 did. Remember that the 777 is an extraordinary aircraft that is revolutionizing air travel. The 767-400 is a stretch of an existing design that is designed to fill a much smaller gap in Boeing's product line than the one that existed between the 767 and 747. The 767-400 probably will not sell more than two or three hundred airframes. But just because Boeing doesn't sell 1200 doesn't mean it's a failure. It will be very profitable for both manufacturer and operator, and has already become very popular with passengers, with its 777 style interior.
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