China doesn’t have a clear timetable for when Boeing Co.’s 737 Max can return to service, though it has been holding talks with the company as well as U.S. and European aviation regulators, the head of the country’s civil aviation authority said.

Feng Zhenglin, director of the Civil Aviation Administration of China, told reporters at a briefing in Beijing that the issue of the grounded Max was “high on our minds” and that there’d been some technical collaboration on the matter with U.S. and European counterparts.

Three criteria need to be met before China allows the Max to fly again, Feng said Thursday. Any change of design needs to approved, pilot training must be efficient, and the conclusions of investigations into the two accidents involving the plane need to be clear and improvement measures effective.

China was the first major jurisdiction to ground the Max following the second of two crashes that killed a total of 346 people in Ethiopia and Indonesia. China’s move in March last year sparked a cascade of groundings in other countries even as the U.S. Federal Aviation Administration said at the time the plane was safe to fly.

U.S. congressional investigators concluded in a scathing report last month that failures by Boeing engineers, deception by the company and significant errors in government oversight led to the two fatal crashes.

Indonesia’s final report on the Lion Air flight that plunged into the Java Sea in October 2018 found that design flaws, FAA certification, aircraft maintenance and pilots’ actions all played a part. Ethiopia has yet to complete its final report on the March 2019 crash near Addis Ababa that killed all 157 people on board, though a 136-page interim report released earlier this year faulted the plane’s design and pilot training.

The Ethiopian government’s chief investigator said last week the goal is to release a final report before the second anniversary of the disaster. The country’s civil aviation authority and Ethiopian Airlines Group will carry out their own safety checks on the model before considering a return.

There were nearly 100 Max planes in operation in China prior to the grounding, making it the biggest market for the jet. The Big Three -- Air China Ltd., China Eastern Airlines Corp. and China Southern Airlines Co. -- are all Max customers, along with about 10 other carriers in the country.

Europe’s top aviation regulator said last week the plane is safe enough to fly again before the end of this year. Patrick Ky, executive director of the European Union Aviation Safety Agency, said China had participated in some of the Max reviews but hadn’t been involved in flight testing.

“I honestly don’t know where they are” with their evaluation, Ky said.

The FAA’s chief Steve Dickson flew the Max in September and said the controls were “very comfortable,” but the review process by the FAA -- Boeing’s main certification body -- isn’t yet complete and it hasn’t commented on when it might return.

While many of the world’s aviation markets are languishing as the coronavirus continues to restrict air travel, China has recovered to around pre-pandemic levels in terms of domestic traffic, so demand for aircraft is relatively healthy.