The 772LR program was recently pushed back, and Airbus is looking at snatching the only customer. So, it's by no means certain the 772LR will fly.
There is also the issue of ETOPS in the NA-SYD flights. If the diversion airfields aren't near enough to the great circle route, the 772 would have to fly a longer route, and if the diversion airfields (which are often small) are closed due to weather, then the 772LR flight gets cancelled but the 345 gets a go-ahead.
If it makes sense for Delta to buy the 345, they'll do so regardless of their relationship with Boeing. We've seen many previously all-Boeing airlines opt to buy Airbus products. Even El Al would have wanted to buy the 332.
There's been no word from either company about a possible order, so this is just a rumour. But it isn't as unbelievable as some people here seem to think.
I don't think the 772LR program is in dire straits quite yet. I think the 772LR program is simply waiting for another customer or two until the go-ahead is given. Any number of airlines could be that customer. Delta, American, and several Asian airlines have expressed interest.
All things being equal, and assuming both models do become available, I think the prudent thing for Delta to do would be to choose the derivative of what they already operate, and that would be the 772LR. The commonality is there, it's the same type rating as the 772ER, and the twin engine economics are unbeatable, especially on flights that long.
Yes, ETOPS does become an issue on flights from the East Coast to SYD, but I don't think Delta is ready to try to go into Australia yet. If and when Delta does attempt an Australia service, I think their only choice is to do it from LAX. Most of the business ties between Australia and the United States center around California. And LAX-SYD can be operated by Delta's existing 777-232ER fleet with ETOPS 180 certification. So I don't think that's a target market for the 772LR.
I agree with your statement that if it simply makes more sense for Delta to buy the A340-500, they will do so. This is a business first and foremost, and if it's a better overall decision to do that, one would hope that Delta would do that. Unfortunately things aren't that simple. Delta has publicly committed to Boeing (737, 757/767, 777) and Bombardier (CRJ) as their sole aircraft suppliers. While Delta is not legally bound to the terms of the Fleet Renewal Agreement they entered into with Boeing some time back, there exists an unspoken agreement by both companies to abide by the terms of the agreement. Delta will buy only from Boeing, and Boeing will give Delta good deals.
Despite Airbus' desire to sell something to Delta, Delta does have an existing business relationship with Boeing and that will definitely be a factor in any decision Delta makes, whether everybody here wants to admit that or not. Everybody talks about the big things like type ratings, fleet commonality, and the like, but for every big thing, there are little things like:
-ground support staff training
-ground support equipment
-cost of insurance
-flight crew training (both cockpit and cabin crew)
In most of these categories, Delta's status as a current 777 operator makes the 772LR a better choice. Delta is heavy into Boeing products, and for Delta's particular needs, it's probably best to stay that way.
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