Airbus is projecting an active secondary market for the A340 family—an outlook that could be bolstered by Rolls-Royce’s (R-R’s) efforts to reduce shop visit costs of Trent 500 engines outfitted on -500s and -600s variants of the four-engine jet.

The airframe manufacturer’s product-support forecast sees about 325 A340s still in service in 2017, down only by about 25 from today’s total. Notably, it expects about 90 aircraft to change hands in the next four years, including 26 A340-500s/600s.

The source of secondhand A340s is no mystery, as long-time operators like Emirates Airline, Lufthansa and SAS have publicized plans to replace them with newer-generation widebodies on order. Where they will end up after being replaced is another matter.

Airbus acknowledges that the A340’s high fuel-burn is an unavoidable issue compared to similar-capacity twinjets. However, the manufacturer says that from a total operating cost standpoint, favorable lease or purchase rates and solid reliability make the A340 a competitive choice for carriers looking to boost long-haul service or add stopgap capacity while planes on order are being built.

Norwegian Air Shuttle is a prime, if extreme, case. When the Boeing 787 was grounded and its deliveries paused earlier this year, Norwegian was one of the carriers affected by the delivery delays. The carrier leased two A340-300s from HiFly to operate routes pegged for the 787. Last week, Norwegian again turned to HiFly and an A340 after grounding one of its two 787s due to persistent reliability issues.

Airbus is confident that Norwegian’s choice will be more the rule than the exception as more A340s become available.

“We are in contact with many customers for those aircraft,” says Airbus Asset Management Marketing Director Marino Modena. “We see there is a market. Today, at competitive lease rates and ownership costs, [the A340] can be a very good competitor on long-haul operations, especially where operators are awaiting delivery for long-haul aircraft.”

The A340’s range and comparable capacity to large twins have helped it maintain a supporting role in many fleets. TAP Air Portugal, for instance, took its first A340 in 1994. It recently upgraded the cabins on its four A340-300s and plans to operate them until replacement A350s are delivered near the end of the decade.

TAP Vice President-Engineering Mario Araujo says the aircraft cost about $1,800 per flight hour and their dispatch reliability is just a shade below TAP’s A330-200s. Fuel burn is higher, of course, and some upgrades—such as Future Air Navigation System avionics—have been avoided to minimize investment in the fleet.

One challenge on the -500s and -600s, which account for more than a third of the in-service A340 fleet and the vast majority of the last airframes built before production ceased two years ago, has been the reported high costs for Trent 500 overhauls performed under R-R TotalCare packages.

The engine maker says it is committed to addressing the issue. “We listen to our customers, and we’re aware of the concerns they have,” R-R Marketing Manager Alistair Forbes said during Aviation Week’s recent MRO Europe Conference in London recently. “We are always looking at ways to make our shop visit costs as low as we can,” and while Forbes said he could not reveal specifics, “we will be trying to find ways to get the costs of Trent 500 TotalCare down.”

Forbes called the Trent 500 “the most reliable engine we’ve ever made,” suggesting that the less-than-expected additional work required during overhauls could play a role in lowering costs for customers.

“Overall, we see Trent 500s as having a good future,” he added. “We’re actively talking to our joint venture partners” like engine shops TAESL and Lufthansa Technik “about how we can keep it going into the future.”

Airbus stands ready to do its part. The manufacturer has extended service goal programs that can push the original A340s past their original design service lives of 80,000 hr. and 20,000 cycles. The latest—certified in July 2012—pushes A340-200s to 134,000 hr. and 25,000 cycles, while A340-300s can go to 156,000 hr. and 31,000 cycles.