BA Boeing Co

BEIJING -- China's aviation regulator has raised concerns about the reliability and security of Boeing Co.'s proposed changes to the 737 MAX jet's software and flight control systems needed to put the plane back in service.

China, the first to ground the 737 MAX jetliner this year, is reviewing the airworthiness of the aircraft in accordance with protocols agreed to by China and the U.S., Liu Lusong, spokesman of the Civil Aviation Administration of China, told a media briefing Thursday.

Ms. Liu didn't specify the concerns.

Mr. Liu said China is sticking to three requirements that it had laid out earlier for resuming the operations of the 737 MAX in the country: Beijing's approval of any design changes, a comprehensive and effective training program for pilots and the publication of clear conclusions on Boeing's investigation into the two fatal accidents that led to the grounding of the jet, along with a plan to avoid future incidents.

A Boeing spokesman said Thursday the company continues to work with the U.S. Federal Aviation Administration, the CAAC and other global regulators to address their concerns in hopes of returning the jets to service.

Boeing's 737 MAX was grounded after two crashes in less than five months killed a total of 346 people. The plane maker has struggled with a final fix to the model's software and flight-control system and is seeking approval from global regulators to get the aircraft back in the air.

China was the first nation to ground the 737 MAX after the second crash, of an Ethiopian Airlines plane, in March. China's commercial airlines had hundreds of 737 MAX planes on order at the time of the crash.

The caution from Chinese regulators could give a further opening to Boeing's competitors. In addition to European rival Airbus SE, which has aggressively courted China's leaders and won some large orders in China, Boeing also faces a homegrown challenger in the C919, which is still being tested ahead of a 2021 rollout and has already secured some orders at home.

Raffaele Huang

(END) Dow Jones Newswires

December 12, 2019 08:55 ET (13:55 GMT)

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