Rescuers searching for the black boxes at the plane crash site in Tengxian County, south China's Guangxi Zhuang Autonomous Region, March 22, 2022. Photo: Xinhua

One of two black boxes from a China Eastern Airlines Boeing 737-800 aircraft that crashed in China’s southern Guangxi Zhuang autonomous region on Monday while Chinese officials released details of the pilots flying the plane.

Investigators were checking whether the discovered black box is a voice or flight data recorder, Mao Yanfeng, director of the civil aviation accident investigation department, said Wednesday in a media briefing.

Black boxes often store audio recordings from the cockpit and data on hundreds of flight parameters including speed and altitude to flap positioning and heading that can help investigators recreate the moments before a crash. 

Mao said there had been “no dangerous weather” on the plane’s route at the time of the crash while the plane’s crew and air traffic control had maintained normal communication before the accident. He said the three pilots on the plane had current licenses, valid health certificates and solid experience.

China Eastern Airlines said the plane had met required maintenance standards.

Because the plane quickly gained altitude before its fatal free-fall into a Guanxi hillside, some aviation experts suggested that the plane could have suffered from mechanical problems. They said pilots could have tried to save the plane by descending to accelerate but a climb-up damaged the plane.

Flight MU5735, carrying 123 passengers and nine crew members, departed from Kunming, capital of Yunnan province, at 1:11 pm on Monday and was scheduled to arrive in Guangzhou, Guangdong province, at 3:05 pm on the same day.

At 2:17 pm, the plane stayed at a normal level and entered the Guangzhou control area. At 2:20 pm, it descended at a high speed and did not respond to the airport traffic control tower messages. At 2:23 pm, it disappeared from radars.

According to footage, the plane dived vertically before it crashed into the ground in Teng county, Wuzhou in Guangxi.

In an instruction issued shortly after the crash, President Xi Jinping, also general secretary of the Communist Party of China’s (CPC) Central Committee and chairman of the Central Military Commission, said he was shocked to learn about the accident and asked for the immediate launch of an emergency response.

He asked authorities to organize all-out search and rescue work and to appropriately deal with the aftermath of the accident. Xi stressed swift action be taken to identify the cause of the crash, and strengthen and overhaul the safety of the civil aviation sector.

Zhu Tao, director of aviation safety at the Civil Aviation Administration of China (CAAC), said in a media briefing on Tuesday evening that it was very difficult to investigate the accident due to the severe damage to the Boeing 737-800 plane.

“We assisted in the search for plane wreck and survivors. Our team did not find any survivors but saw relatively large pieces of plane wreck, and bodies,” Ou Ling, a political member of the firefighter and rescue team in Wuzhou, told China Central Television (CCTV), a state-owned broadcaster controlled by the CCP, on Tuesday morning.

Citing the CCTV report, many Chinese news websites reported on Tuesday that bodies had been found. Sun Shiying, chairman of China Eastern Airlines Yunnan branch, said at a news briefing on Tuesday night that no survivors have been found so far. CAAC officials reiterated the official line.

Since then, major news websites have removed their “bodies found” articles from the Internet while some others still have Ou’s quote published on their sites.

Zhang Zhonglin, a Chinese aviation worker, wrote in an article published by Guancha.cn that none of the 132 people on the plane could have survived the crash. Zhang said as the plane had climbed up after its sudden descent, the possibility of a hijack or an intended crash could be ruled out.

A Chinese pilot surnamed Gao, who has 26 years of flying experience, told the media that it was important to find out what had happened in the plane in the first 16 seconds during the two minutes before the crash. Gao said the plane was flying horizontally but slowing during the 16 seconds for unknown reasons.

He said pilots had tried to accelerate the plane by flying downward but the plane could not survive the huge pressure during a climb-up. Chinese investigators said they would make a conclusion after both black boxes of the plane were found.

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