Boeing Co said on Thursday it had resumed flight testing of its 777X jets after an inspection in October found an engine issue.
GE said last month it was reviewing a technical issue that occurred during GE9X post-certification engineering testing of the plane, and had decided with Boeing to remove the engine and send it to a test facility in Ohio for engineering test runs.
The 777X, also known as the 777-9, is a larger version of the 777 wide-body jet and has been in development since 2013.
Certification is needed before Boeing can begin deliveries.
In May 2021, the FAA told Boeing that, realistically, it would not certify the 777X until mid- to late 2023 and rejected a request by Boeing to clear a certification hurdle, citing numerous concerns about lack of data and lack of a preliminary safety assessment. The 777X had previously been expected to be released for use in June 2020.
Congress approved a sweeping certification reform bill in late 2020 after two fatal Boeing 737 MAX crashes that had added new requirements to getting aircraft approved.
Boeing Chief Executive Dave Calhoun said in April that it is "definitely a more rigorous process that we're all going through" to get airplanes certified.