Boeing 737 Max airplanes Photo: VCG

Major safety concerns raised by China's civil aviation regulator over US plane maker Boeing's 737 MAX have not been fully addressed, an official with the Civil Aviation Administration of China (CAAC) said on Monday, when asked about the timetable for the jet to return to service in the market.

"From the current situation, the major safety concerns that were raised by the CAAC has not been fully met, and for this reason, relevant technological review has not entered the certified airworthiness phase," Dong Zhiyi, deputy head of the CAAC said at a Ministry of Transport press conference on Monday in Beijing.

However, Dong said that Chinese regulator is in contact with the US plane maker and the US Federal Aviation Administration (FAA), and are working in a positive and systematic manner, including conducting a full and thorough review for recertification of the aircraft.

"Later procedures in obtaining certified airworthiness will be carried out according to plan and in a steady fashion after the Chinese concerns are addressed," Dong said.

Boeing 737 Max was grounded in March 2019 following two deadly crashes in the world that happened within half a year and claimed 346 lives.

CAAC has set three principles for the jet to return to service in China - design changes need to be certified, pilots need to receive proper training and effective improvements need to be made to address the specific findings of investigations into the two crashes.

The statement by CAAC came as some countries have moved to lift their bans on the aircraft but new concerns have since come to light.

The US Transportation Department's inspector general last week faulted "weaknesses" in US government's certification of the aircraft with a 63-page report saying the FAA did not have a complete understanding of a Boeing safety system tied to both crashes and said "much work remains" to address some outstanding issues. The department cited "management and oversight weaknesses" in its report.

China was the first country to ground the Boeing aircraft in 2019.