Airbus is once more rewriting its plans for the A350XWB, delaying entry into service of two models while promising much improved performance on the largest version in the family of twin widebodies.

The A350-800 now will not be fielded until mid-2016, two years later than planned, and the -1000 will only emerge in mid-2017, about 18 months later than customers have been promised, although Airbus officials insist the design changes will yield a much improved product. It is the third time Airbus has made major changes to its A350 plan since it first tried to determine how to tackle Boeing’s 787.

It is not just higher performance that is causing the schedule delay, however. Airbus is trying to free industrial resources to ease development pressure on the already late A350-900, the first of the aircraft family due to be fielded, and develop the A320NEO (new engine option). “We are quite stretched” in some areas, concedes Airbus chief operating officer Fabrice Bregier, pointing to stress engineers and composite specialists. The delay, particularly on the -800, “relaxes a little bit the constraints on key resources,” he notes.

The -800 adjustment was made possible because many customers for the type have migrated to the -900, says John Leahy, Airbus COO for customers. That means that no customers were due to receive the aircraft until mid-2016, so the delay has no direct customer impact. Bregier insists that if there had been customers in early 2016, the product could have been ready in time. Company officials dismiss the notion they may abandon the -800 outright. First flight of the type is expected in 2015.

The centerpiece of the adjustment is the A350-1000, with which Airbus is trying to attack the Boeing 777-300ER. The main feature of the change is increasing the thrust of the Rolls-Rocye TrentXWB engine to 97,000 lb., 4,000 lb. more than forecast. The change allows Airbus to offer 400 naut. mi. more range at a maximum passenger weight of 4.5 metric tons on a 6,000 naut. mi. route. The change prompts Leahy to boast that the -1000 “does more than the 777-300ER does and it does it with 25% less fuel consumption.”

Boeing has long said it is ready to improve the 777, but has held off on defining the update until Airbus more clearly spells out its plans. That strategy now appears to have worked out, giving Boeing more time to continue selling the profitable widebody and figuring out how to respond.

Boeing Commercial Airplanes President Jim Albaugh said on June 16 that both smaller and larger improvement packages for the 777 are being considered depending on what its rival does.

The higher performance for the TrentXWB powering the A350-1000 will come with “absolutely no fuel burn deterioration” over what was promised, says Mark King, the Rolls-Royce president for civil aerospace. The upgrade is built around better than expected performance on early build TrentXWB-84s for the -900, allowing the engine maker to tweak the performance. Some program details are still being defined, King says, but the size of the core will be scaled up slightly to increase air flow. What is more, the heat management will be improved and the new version also will showcase improved materials and tip clearance control. The fan will remain 118 inches in diameter.

Airbus has promised Rolls exclusivity on the -1000 as part of the additional investment the engine company is having to make.

Aircraft changes include a 10 metric ton increase in maximum takeoff weight, and the addition of five aft fuselage frames and six front fuselage frames, as well as structural reinforcements, says Bregier. The wing will also be longer with a longer trailing edge of around 300 mm and new high lift controls and actuators. The capacity of the air conditioning system also has to increase.

Moreover, Airbus is looking to use the extra time to mature some technologies for later introduction, such as composite door frames to replace titanium ones.

The only big supplier change is the main landing gear, which Airbus put out for bid and Goodrich won over Messier-Dowty. The main landing gear will feature six wheels rather than four, a change that was forecast already for the -1000.

The price of the aircraft will also increase, with list price going up $9 million from $299.7 million for the -1000 at 2011 catalogue price. Still unclear are some of the cost considerations of the changes, including whether existing -1000 customers would have to pay the new price. Etihad has ordered 25 of the aircraft, Qatar and Emirates 20 each, and Asiana 10. Also unclear is if the airlines would be owed delay penalties. Bregier says the cost of the -1000 development program should not be much higher than the $2.4 billion earmarked for the effort.

Meanwhile, the -900 program is moving to the start of final assembly around year-end, with the goal of completing the first flight toward the end of 2012 and first delivery at the end of 2013. The program has inched further to the right, but Airbus so far has managed to avoid a slip of first delivery into 2014, although many industry officials expect that still to happen.

Airbus currently has 574 orders for A350s from 36 customers (359 for the -900, 140 for the -800, and 75 for the -1000).