WSJ News Exclusive | China Eastern Black Box Points to Intentional Nosedive

“The plane did what it was told to do by someone in the cockpit,” said a person who is familiar with American officials’ preliminary assessment, which includes an analysis of information extracted from the plane’s damaged flight-data recorder.

Also underpinning the American officials’ assessment, this person said: Chinese authorities, who are leading the investigation, so far haven’t flagged any mechanical or flight-control problems with the plane involved in the March 21 crash in southern China. That model is a workhorse of the global aviation industry and is part of a family of Boeing aircraft that have one of the best safety records in commercial flying.

The information gathered so far in the China Eastern probe has led U.S. officials involved with the investigation to turn their attention to the actions of a pilot, people familiar with the matter said. There is also a possibility that someone else on the plane could have broken into the cockpit and deliberately caused the crash, these people said.

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Boeing Co.

nor air-safety regulators have been working on any service bulletins or safety directives stemming from the crash, people familiar with the matter said. Such messages would be used if authorities believed there was a need to alert airlines and pilots to problems the flight crew encountered in the accident or detail needed fixes to the aircraft.

Accident investigations can turn up previously unknown evidence that can bolster or undermine preliminary assessments. One person familiar with the U.S. officials’ preliminary assessment said the Americans don’t have all information available to their Chinese counterparts.

The U.S. officials’ preliminary assessment hasn’t been reported before. In April, the trade publication Leeham News and Analysis reported that an initial readout of the China Eastern plane’s flight-data recorder suggested deliberate pilot inputs into the controls.

China Eastern, in a statement to The Wall Street Journal, said no evidence has emerged that could determine whether or not there were any problems with the aircraft involved in the accident. The airline repeated its senior official’s statement from March that the pilots’ health and family conditions were good, and added that their financial status was also in good shape.

The airline said it wasn’t responsible for the accident investigation and referred to official announcements, including the Chinese government’s summary of its preliminary report released on April 20. The summary said that data restoration and analysis of the damaged black boxes was still in progress.

“Any unofficial speculation may interfere with the accident investigation and affect the real progress of the global air transport industry,” the airline said.

The Civil Aviation Administration of China, the country’s air-safety regulator, didn’t respond to faxed requests for comments and didn’t pick up calls. The agency hasn’t commented on any potential causes of the crash and said last month investigators continued to probe the accident.

Asked about a possible cockpit intrusion, China Eastern said such a scenario wasn’t plausible. The airline cited information from a March 25 news conference in which Chinese authorities said no emergency code had been sent from the plane before the crash.

After grounding its entire fleet of the same Boeing model for about a month following the crash, China Eastern began putting its other 737-800s back into passenger service. China Eastern said that it continued to inspect aircraft that were manufactured around the same time as the plane involved in the crash.

The 737-800 preceded Boeing’s 737 MAX model, the latest variant of its long-serving narrow-body jet. MAX jets haven’t returned to commercial flights in China more than three years after two fatal crashes in other countries that were tied to a faulty flight-control system.

Chinese authorities haven’t indicated to their American counterparts when they might communicate their official determinations from the probe publicly, people familiar with the matter said. The CAAC has said it would make any significant developments in the investigation public in a timely fashion.

The CAAC completed a preliminary investigative report about the crash, as is expected under an international aviation treaty. The Chinese agency didn’t release the document, but provided a summary of the findings, in which it said that communications between the crew and air-traffic controllers didn’t indicate anything abnormal before the plane descended. Air-traffic controllers tried to contact the plane after they saw it drop but got no response, it said.

Accident-investigation agencies can take about a year or more to issue their final conclusions about a crash’s causes and contributing factors. In some previous accident investigations, international authorities have disagreed over whether someone crashed planes intentionally.

The crash of China Eastern Flight 5735 posed a fresh challenge for aviation authorities in the country, which has maintained a strong flight-safety record in recent years. Before the accident, China’s last fatal crash occurred a dozen years ago, and the latest crash marked the deadliest air disaster in China since 1994. China Eastern said in its statement that it has flown safely for 18 consecutive years.

The China Eastern plane disintegrated when it hit the mountain, scattering debris across wooded and rugged terrain. Search-and-rescue teams didn’t find any survivors.

Passengers who lost their lives included a 17-year-old boy on his first flight, six people traveling together for a funeral and a former accountant who had recently moved to start a new job with e-commerce company Alibaba Group Holding Ltd. and marry his sweetheart.

In late March, a team of firefighters found the jet’s flight-data recorder buried several feet underground about 130 feet from where the plane crashed. Data captured by that device, as well as by the cockpit voice recorder, which had been found earlier, are expected to play important roles in helping authorities determine the cause of the accident.

Write to Andrew Tangel at Andrew.Tangel@wsj.com and Micah Maidenberg at micah.maidenberg@wsj.com