July 13 (Reuters) - Boeing ( BA ) has started

certification flight testing of its long-delayed 777-9 with U.S.

aviation regulators onboard, the U.S. planemaker said in an

emailed statement.

The company said it conducted its first flight on Friday

night after receiving Type Inspection Authorization (TIA).

The development is a boost for Boeing ( BA ), which has been

grappling with production and legal issues since a Jan. 5

mid-air panel blowout on a 737 MAX plane.

The news was first reported by Air Current.

The U.S. Federal Aviation Administration (FAA) did not

immediately respond to a Reuters request for comment out of

office hours.

The 777-9 is part of the 777X project to upgrade the 777

wide-body jet. The project has been in development since 2013

but has faced multiple hold-ups, including certification delays.

Type inspection authorization is typically associated with

the start of the certification process, made after the FAA has

examined technical data. The milestone allows FAA pilots to

participate in flight testing needed to certify the plane for

normal operation.

The chairman of Emirates, the plane's biggest customer, said

in May he did not expect the certification before the first

quarter of 2025.

Boeing ( BA ) has said that the 777-9 test fleet will undergo the

most thorough commercial flight test effort the planemaker has

ever undertaken.