Editor’s note: The video above is from a 777X taxi test at Everett’s Paine Field.

Boeing suspended what was supposed to be the final load testing on the new 777X airplane after crews encountered an “issue” during the test.

Final load testing is the last part of a series of tests Boeing has been conducting on the full-scale test airplane, according to a Boeing spokesperson. The test is meant to put the airplane under stresses well beyond normal operational loads.

The 777X static test airplane, which is a test plane used for structural certification testing, was on the ground when the issue occurred, the spokesperson said.

KING 5 has learned the test was inside of a building and force is added until the airplane collapses. It appears a door inside the fuselage had an issue before crews got the airplane to the point they wanted to, and the test was suspended.

Also see | Boeing 777X jet undergoes 1st taxi test at Paine Field

“The testing conditions were well beyond any load expected in commercial service. The event is under review and the team is working to understand root cause,” the spokesperson said.

The Boeing 777X is still in development and is the first airliner with folding wingtips. The outside 12 feet of each wing can fold up, allowing the jet to get into airport gates. The plane’s overall wingspan is 235 feet.

Earlier this year the giant plane made taxi runs at various speeds at Everett’s Paine Field and tested the jet’s brakes.

It was hoped the plane would be making its first flights by now. However, General Electric, the exclusive supplier of the 777X’s massive new engines, said they have to work on a “durability issue” found during testing in Ohio.

Boeing said in June that the first flights were likely to occur in the fall.

Also see | First flight for Boeing 777X on hold until engine issues resolved