‍DALLAS — Boeing’s fourth 777-9 test aircraft, WH004, took flight on Wednesday from Paine Field (PAE) in Everett, Washington, for the first time since 2021. This airframe is unique as it is the only one in the 777X test fleet equipped with a full passenger cabin.

With all four 777X test aircraft in the air, Boeing has moved forward on the type’s certification path. WH004, with its complete passenger cabin, will play a crucial role in testing essential cabin systems. 

This testbed will evaluate factors like air circulation, noise levels, and overall comfort, critical to ensuring a smooth passenger experience on future flights.

Back in Action: Preparing WH004 for Flight

Over several months, Boeing teams performed extensive maintenance and preparations to bring WH004 back into flight-ready condition. The aircraft had been placed in storage to allow earlier testing phases to focus on the other three 777-9 test jets.

“Although reactivating the airplane involved a significant number of updates, our team remained committed to first-pass quality,” said Levi King, Flight Test Maintenance lead, via onfirstup.com. “It’s incredibly rewarding to know that our efforts are helping move this important program closer to certification.”

WH004’s return marks meaningful progress as Boeing continues toward 777X certification and eventual entry into commercial service.

Boeing 777-9 Flight Testing Progress

Boeing's flight testing for the 777-9 is actively underway, focused on validating the aircraft's safety, reliability, and performance. Since January, the team has conducted tests across various locations, including Puget Sound, Curacao, Montana, New Mexico, Oklahoma, Texas, and eastern Washington.

So far, Boeing has completed over 1,400 flights and accumulated nearly 4,000 flight hours. These extensive tests are crucial for ensuring the 777-9 meets all safety and performance standards required for U.S. Federal Aviation Administration certification.