* Airbus A350 certification plan on track, regulator says
* EASA expected to approve 180 ETOPS for Airbus A350
* EASA chief defends certification method for upgraded jets
* EASA to thoroughly vet folding wingtips on Boeing 777X (Adds Airbus comment)
By Tim Hepher
PARIS, May 7 (Reuters) - Airbus is on track to get safety certification for its latest jetliner, the A350, by "the end of the summer" as planned, Europe's top air safety regulator said on Wednesday.
Airbus has said tests are going well on its new lightweight, medium-sized jet, developed at an estimated cost of $15 billion and designed to compete with Boeing's 787 Dreamliner, the world's first mainly carbon-composite passenger jet.
"We are still looking at the end of the summer," Patrick Ky, executive director of the European Aviation Safety Agency (EASA), told Reuters.
Backing for the timetable came as Airbus prepared for extreme weather testing in Florida where a special hangar will bathe the jet in temperatures between -40 and +40 degrees Celsius.
EASA is seen likely to certify the jet at the end of August or in early September so that Airbus can deliver the A350 to its first customer, Qatar Airways, around the end of the year.
The A350 and 787 Dreamliner are competing for thousands of projected sales in the lucrative market for lightweight intercontinental jets seating between 250 and 350 passengers.
While European and U.S. regulators most often work in tandem, safety officials say there will be a gap of several months between transatlantic approvals needed to allow the A350 to fly on routes involving long stretches over water.
The Extended Operations or ETOPS rules determine the maximum amount of flying time planes can stray from the nearest airport. Airbus has asked for a margin of at least three hours, matching the current rule for the 787.
Sources say EASA's certification plan calls for 180 minutes ETOPS from the outset, but the U.S. Federal Aviation Administration (FAA) may take a few months longer to consider the same level of clearance.
Industry experts say this will not immediately disrupt deliveries since the first few A350s are earmarked for airlines that operate Airbus aircraft delivered under EASA certification.
But Airbus will need to meet the same rules for the FAA before delivering to airlines in parts of the world where the FAA takes the lead.
Airbus said it aimed for EASA and FAA approval for "beyond" 180 ETOPS from the outset. The FAA had no immediate comment.
ETOPS qualifications are central to the business plans for the rival carbon-fibre jets, both designed to fly efficiently and reliably on two engines where some older planes used four.
Boeing said last week the FAA was considering an application to lift the 787's ETOPS margin to 330 minutes. Airbus will also ultimately seek a progressively higher ETOPS rating.
DEALING WITH DERIVATIVES
Facing budget constraints, regulators rely on planemakers to validate parts of their own work, a practice that came under fire after the 787 was grounded over battery problems last year.
Some industry watchers have also criticized regulators for allowing planemakers to use existing safety certificates when redesigning earlier models, a process known as grandfathering, rather than seeking a costly brand-new certification.
The issue is increasingly in focus as the world's largest planemakers rely on such updates, with the A350 and 787 seen as their last all-new jetliners for at least a decade.
Europe's recently appointed safety chief defended the practice of amending safety certificates for upgraded jets.
"It makes sense to focus on new topics ...and critical components," Ky said, adding, "We never compromise on safety."
EASA will focus mainly on "significant changes" when examining Boeing's latest upgrade, the 777X, he said.
It will pay particular attention to plans for folding wingtips, designed to offer a long wingspan while still fitting into existing parking spaces when the jetliner is on the ground.
The Boeing 777X is due to enter service in the middle of 2020 and is an enhanced version of Boeing's most popular wide-body jet, which has been in service for two decades.
Boeing officials said last week they hoped the revamped airplane would not need a completely new certification process, and that they would seek an amendment to existing approvals. (Additional reporting by Alwyn Scott, Editing by Lionel Laurent and Andrew Callus)