Luke,
as you probably know, the PMNW fleet is composed of two "generations" of aircraft - the majority are around 20 years old and the rest are closer to 10 years.
Replacing the interiors on these aircraft could well be close to a $10M job so DL is not likely to do it unless the planes will fly for 5 or more years. (and that holds true for major mods on other fleet types - part of why they are not moving forward w/ AVOD on the 320s and more of the 757 fleet since large portions of both of those fleets could be replaced in 3-5 years w/ the 739 order).
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The 744 is not a terribly fuel efficient aircraft compared to newer technology aircraft like the 77W but DL/NW have reported fairly competitive CASMs on the 744 to the DOT, partly because the aircraft in NW's config were fairly high density. NW also obtained very good lease rates on most of the 744s in BK.
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I think a large factor in getting rid of these aircraft will be that they are too large in the winter. You can tell from DL's financial reports that they have done a very good job of increasing revenue in the Pacific, both by strengthening the NRT hub w/ new service and feeding more traffic over existing routes, but also because of the new DTW and SEA to Asia flying; both sets of new routes have posted very healthy revenue numbers w/ the DOT.
But it is very hard to keep all of the new capacity in place plus maintain the NRT hub during the winter when demand falls off; even though the new nonstops are generating good yields, DL has to pull them down in order to keep the NRT hub intact year round.
Thus, traffic that could fly at higher fares over the new DTW and SEA routes is forced to fly through NRT at lower fares.
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The strong yen has helped DL increase the percent of Japan local traffic but DL mgmt knows this won't continue forever... thus it becomes necessary to keep a sustainable level of flow/local traffic at NRT year round as well as continue to develop and maintain nonstop flights from the US mainland to points throughout Asia; UA now has 3 US gateways/hubs from the US to China all of which maintain year round daily service so DL must be able to compete on a reasonably comparable basis - and UA also has the NRT hub option.
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As you probably know, DL is putting the 332 on DTW-HND as of next spring when it restarts which indicates that they are moving forward w/ the performance improvement package and whatever cockpit crew rest facilities are necessary to satisfy ALPA on 12+ hour flights. But it adds 10 12+ hr aircraft to the fleet and the 332 w/ the PIP is capable of 14 hr flights. The 763ER lie flat/winglet program is moving forward and that aircraft is good for almost 13 hr flights. The 332 becomes capable of flying from the midwest to Japan and both the 332 and 763ER can fly much of NE Asia from SEA - or Japan from LAX. With both aircraft, DL is able to move forward w/ fragmenting the Pacific just as the 763ER did over the Atlantic; hubs become less important and the ability to overfly NRT increases.
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There was also talk for a number of years that DL was interested in acquiring used 772ERs which are supposed to eventually get winglets; DL calculates that like the 763ER, the cost of operating the 777ER is not than much less than newer technology aircraft like the 787 when you factor in the cost of the debt associated w/ acquiring newer technology aircraft.
DL and NW have both long believed that it is cheaper to acquire used aircraft one generation old, refurb them, and operate them for 5-10 more years than it is to buy new current generation aircraft.
With the new interiors, the 767 and 777 are competitive from a passenger perspective with any new generation aircraft.
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DL is not about to give up its position at NRT and w/ smaller aircraft, DL can continue to operate every one of its existing slots... but it might be on smaller aircraft with a higher percentage of local Japan traffic while smaller aircraft than the 744 will be used across the Pacific from the NRT hub. By reducing the amount of flow traffic through NRT, DL can maintain its current market share in Japan even though it will use smaller aircraft. The new HNL-FUK route demonstrates that there is a lot more of Japan that can be opened/reopened using smaller aircraft.
