The European planemaker, part of EADS (EAD.PA), announced the move as the influential Gulf airline said it preferred the two largest models of A350 for its business model, confirming a trend towards more seats to cope with regular increases in passenger traffic.

The A350 comes in three models - the two smallest compete with Boeing's 787 Dreamliner while the largest, the 350-seat A350-1000, aims for a crucial niche dominated by the 777.

Many experts see the lucrative market for jets just below 400 seats as the next major battleground between the world's top planemakers. Boeing is looking at revamping its 777 design.

Airbus said Qatar Airways had upgraded its order for the largest A350-1000 variant to 37 planes from 20 and increased its order for the base model, the A350-900, by three planes to 43, confirming what aviation sources had previously told Reuters.

However these are not net new orders, since the same airline has scrapped an order for the A350-800, the smallest variant which faces speculation about its future due to weak sales.

The upgraded order will net Airbus an extra $2.8 billion at list prices. In volume, Qatar's A350 order remain at 80 units.

Qatar Airways is the launch customer for the future A350 and is also a major user of the 777, Boeing's most profitable plane.

WINGTIP DEVICES

Airbus said separately it had won approval from European authorities to deploy drag-reducing wingtip devices that will allow airlines to cut fuel bills by more than it had expected.

The so-called sharklets, which are made from composite materials and are 2.4 metres tall, are upward-slanting wingtips designed to help narrowbody A320 aircraft fly further on the same amount of fuel.

"The certification of Airbus' sharklets is a milestone which paves the way for airlines to benefit from savings in fuel of around 4 percent," Tom Williams, executive vice president of programmes at Airbus, said in a statement.

"That's better than we'd anticipated."

Airbus had previously targeted a net fuel saving of 3.5 percent with the devices, part of a package of improvements that together with new engines are designed to save airlines about 15 percent in fuel bills on the future revamped A320neo plane.

The approval applies to Airbus' A320 family of planes powered by CFM56 engines from CFM International, a venture between General Electric (GE.N) and France's Safran (SAF.PA).

Airbus has also been testing the sharklets on A320s powered by International Aero Engines' V2500 engine.

Airbus and U.S. arch-rival Boeing are focusing on wing enhancements as key selling points for their latest revamped models, with tens of billions of dollars of sales for both firms at stake each year. (Editing by Mark Potter and David Holmes)

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