That the very large aircraft market has its limits has long been recognized by Boeing and Airbus. But five years after entry into service of the Airbus A380 and two years after the Boeing 747-8F was first delivered, even their existing backlogs appear to be partially under threat.

Boeing has listed 108 firm orders and 37 deliveries for the 747-8 and -8F, leaving it with a backlog of just 71 aircraft. The situation looks more comfortable for Airbus, which still has 165 outstanding deliveries for the A380. But, in spite of the wing-rib-feet redesign slowing production next year, its output is still much higher.

One factor also cannot be disregarded in the A380 figures: More than one-third, 62 aircraft, are still to be delivered to the single largest operator of the aircraft, Emirates, which has left no doubt that it will take the outstanding jets as part of its huge expansion plans. But of the 103 other orders, there are several commitments for 23 aircraft with big question marks.

Most immediately, an order for 10 aircraft placed by Hong Kong Airlines will likely be converted very soon to much smaller A330s. The carrier has indicated it plans to pull out of the long-haul market and focus on regional flying, for which it appears the A380 will not be the right-sized aircraft. There have been allegations that the order conversion might be linked to China's opposition to the European Union's Emissions Trading System (EU ETS), much like another commitment for 35 A330s that are to be allocated to several Chinese airlines. The fact that simple market concerns are driving Hong Kong Airlines away from the A380 gives Airbus little comfort.

Another dubious order is Kingfisher Airlines' commitment for five aircraft. The airline has been grounded since early October, after flight crews went on strike for not having received salaries for months. Part of its current fleet is impounded. Even if efforts to resurrect Kingfisher succeed eventually—which would likely involve a new foreign minority shareholder such as Etihad Airways—it is doubtful if Kingfisher could support operations of five A380s, even in the long term.

Much less dramatic cases give Airbus reason to be worried, too. Virgin Atlantic's outgoing chief executive, Steve Ridgway, says the airline will not take its six A380s on order before 2017, if at all, and he questions whether Virgin could ever viably operate such a small sub-fleet. It is too early to tell what influence Delta Air Lines' new 49% stake in the British carrier will have. While the planned transatlantic joint venture is likely to drive more passengers into Virgin's aircraft, Delta is not particularly keen to operate very large aircraft. It inherited a fleet of Boeing 747-400s in its merger with Northwest Airlines, but they do not seem likely to be replaced by a similarly sized or even larger aircraft type.

Qantas has eight more A380s to be delivered and has not indicated that it might not take them all, despite suffering huge losses in its long-haul operations. However, it has deferred to 2016 and 2017 two that were due to be delivered in 2013, and it has pushed back beyond 2019 the remaining six, which also has freed up earlier production slots in Toulouse.

John Leahy, Airbus chief operating officer customers, says there are two A380 slots available by the end of 2015 and a few more in 2016. “I'm not concerned right now,” Leahy tells Aviation Week. But at any given time, he says he would like “to have around two years of production” as a backlog. He points out that potential A380 customers often do not want to wait several years for deliveries, thus ordering rather late.

Airbus has delivered 92 A380s to nine customers serving 73 routes and 32 airports. It plans to hand over 30 aircraft this year, although it collected only four firm orders in 2012 (from Transaero Airlines). It also signed a letter of intent for five more with Singapore Airlines, and while that commitment has yet to be firmed up, Leahy predicts it will be before year-end, bringing the 2012 A380 orders total to nine. Leahy also hints that he is talking with another customer that could place a “significant order” before Dec. 31, but that commitment would be initially a memorandum of understanding.

Next year, A380 production will drop to fewer than 30 aircraft per year because of the introduction of fixes to the wing, but Airbus says that it will average 30 per year over the next two years. It eventually targets a rate of four aircraft per month. Even at that rate, the current backlog would be sufficient for more than three years of production; at the slower output, it is equivalent to over four years, not counting cancellations from Hong Kong Airlines and Kingfisher.

Leahy says he is still convinced “that we made the right decision” in building the A380. He expects demand to improve next year and “certainly” in 2014. He attributes the current market weakness to legacy airlines being more affected by the downturn than low-cost carriers, which have placed most of the big orders for other models such as the Boeing 737 MAX and Airbus A320NEO. But he asks, “how are we going to double [revenue passenger kilometers] in the next 15 years,” other than by using larger aircraft?

Unlike the A380, which is tied solely to the fortunes of the high-capacity passenger market, the 747-8 backlog mostly consists of freighters, making it largely beholden to the ups and downs of the international air cargo business. Having recently sustained the loss of five valuable 747-8F orders from the leasing unit of Dubai Aerospace Enterprise (DAE), Boeing acknowledges that the cargo market is battling tough times.

With the DAE cancellation, Boeing is left with net firm orders for just two 747-8Fs in 2012, following orders for five from Air China and two from an unidentified customer. The result is that, after 37 deliveries and despite Boeing's best sales efforts, the firm-order backlog has shrunk to 71, or just under three years of production at the current rate of two per month.

Launch customer Cargolux has already taken seven of 13 747-8Fs on firm order, but it is searching for a new strategic partner after Qatar Airways indicated it wants to sell its 35% stake. The two carriers have clashed on strategy issues, particularly Qatar's proposal to convert some of the 747-8 orders into those for the much smaller 777F.

The Cargolux case highlights a fundamental concern about the 747-8F: It is a very large freighter and, with cargo markets in a crisis mode now, there are few who can afford it. “The aircraft is simply too big for us,” says one airline CEO, who has both considered buying the type and looked at investing in Cargolux.

Yet Boeing has no plans to change the production rate and maintains its faith that the 747 freighter and passenger model market will return to health in the longer term. However, with deliveries outpacing orders, will that occur in time to sustain the 747-8 production line? The answer is “yes,” according to 747 Vice President and General Manager Elizabeth Lund, who says that despite the current market softness, freight operators continue to take delivery of the more efficient, newer models while grounding older, less economical ones such as converted 747-400BCFs.

In the short term, Lund notes that the order hiatus is allowing Boeing to burn off its backlog which, thanks to the program's earlier delays, swelled to a large size. “We're pleased with the 37 [deliveries] over 14 months,” she says. Nine were handed over in 2011 and the balance in 2012. Of these, all but 10 have been freighters: Four passenger models were delivered to launch customer Lufthansa and six to completion centers for eventual use as business jets.

Part of Boeing's optimism is built on the raft of upgrades and improvements that will be rolled into the 747 by 2014. The manufacturer has committed to reducing the operating empty weight by 6,500 lb. but is looking for more. “We're on our way to a 10,000-lb. weight reduction,” says 747-8 Chief Project Engineer Bruce Dickinson. “We've taken the lower-hanging fruit for the first 5,000 lb.,” he adds. Some elements such as a lighter thrust reverser will be retrofittable, though Dickinson says other weight-saving structural improvements, such as modified washers and sealants, cannot be easily changed after assembly.

Additional aerodynamic, propulsion and systems improvements are also in the pipeline for introduction in 2014. Chief among these will be the General Electric GEnx-2B performance improvement package, which is designed to bring a 1.6% improvement in fuel burn for introduction into service by the end of 2013 (see page 36). This could rise even more, says Dickinson. Other improvements are in hand for the flight management computer (FMC) to incorporate features such as required navigation performance and a “quiet climb” function. The FMC 3.0 load is scheduled for the end of 2013.

A big-ticket upgrade remains the activation of the 747-8 passenger model's 3,300-gal. tailplane fuel tank. This was disabled before the first aircraft entered service after analysis indicated that, under certain fuel load circumstances, the tail tank could induce flutter. The first parts are now being built for the modified system, which will be introduced with other improvements in early 2014.

Reactivation of the tail fuel tank is a key enabler to improving the aircraft's performance, says Lufthansa 747-8 Chief Pilot Elmar Boje. Although the extra fuel provides additional range, Lufthansa is also keen to use the increased aft weight to assist in trimming the 747-8 to lower cruise drag. The 747-8's fuselage extension “tends to be nose-heavy so we might gain performance,” Boje says. Lufthansa also plans to ask Boeing to study minor software changes to the fuel transfer system that would lengthen the amount of time the fuel is in the aft tank.

All the improvements are due to be flight tested next year. Lufthansa is due to take another five 747-8s in 2013, and 10 more, all with the lighter structure and improved systems and engines, are due for delivery by the end of 2015.

Boeing 747-8 Orders/Deliveries
Air China 5/0
Arik Air 2/0
Atlas Air 9/6
VIP aircraft 9/6
Cargolux 13/6
Cathay Pacific 10/8
Gecas 2/0
DAE (order canceled last week) 5/0
Korean Air 12/2
Lufthansa 20/4
Nippon Cargo Airlines 14/1
Unidentified 2/0
Volga Dnepr 5/3
Source: Boeing
Airbus A380 Orders/Deliveries
Air Austral 2/0
Air France 12/8
Asiana 6/0
British Airways 12/0
China Southern 5/4
Emirates 90/28
Etihad 10/0
Hong Kong Airlines 10/0
Kingfisher (airline is grounded) 5/0
Korean Air 10/5
Lufthansa 17/10
Malaysia Airlines 6/4
Qantas Airways 20/12
Qatar Airways 10/0
Singapore Airlines 19/19
Skymark 6/0
Thai Airways 6/2
Transaero 4/0
Virgin Atlantic (deliveries pushed further out) 6/0
Sources: Airbus