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Boeing's ( BA ) long-delayed 777X resumes flight testing after

five-month hiatus

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Boeing ( BA ) first planned to deliver 777X in 2020, now slated

for

2026

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Customers include Emirates, Qatar Airways, Lufthansa,

Singapore

Airlines

SEATTLE, Jan 16 (Reuters) - Boeing ( BA ) resumed

testing for its long-delayed 777X widebody jet on Thursday, with

the first flight since the U.S. planemaker grounded the test

fleet in August due to the failure of a key engine mounting

structure.

The grounding came just five weeks after it had started

certification flights for the 777-9 with officials from the U.S.

aviation regulator onboard.

Federal Aviation Administration staff were not on board for

Thursday's flight, according to the company.

The 777X is the successor to Boeing's ( BA ) 777, one of the most

commercially successful long-haul airliners. The company

initially planned to deliver the first 777X to launch customer

Qatar Airways in 2020.

First delivery of the 777-9 has since been pushed back

to 2026, followed by the smaller 777-8 and a freighter version

later in the decade.

Boeing's ( BA ) other 777X airline customers include Emirates,

Lufthansa, Singapore Airlines and Cathay

Pacific Airways ( CPCAF ). The planemaker has 481 777X orders,

including 170 from Emirates and 60 from Qatar, according to

Cirium, an aviation industry analytics company.

Boeing's ( BA ) 777-9 test plane made a return flight from Boeing

Field in Seattle to Moses Lake, Washington on Thursday.

"We continue to execute a rigorous test program to

demonstrate the safety, performance and reliability of the

777-9," Boeing ( BA ) said after it landed in the afternoon.

A company spokesperson declined to comment on how the

airplane performed during the flight.