The pilot of the China Eastern Airlines flight that crashed in southern China with 132 people aboard was an industry veteran with more than 6,000 hours of flying time. His co-pilot was even more experienced, having flown since the early days of China’s post-Mao era, training on everything from Soviet-model biplanes to newer Boeing models.
Together, the men operating Flight 5735 had more than 39,000 hours of flying experience, the equivalent of four and a half years nonstop in the cockpit, adding to the mystery of why the plane plunged from a cruising altitude of 29,000 feet into a wooded mountainside on Monday.
How they piloted the Boeing 737 will be closely examined as investigators seek to explain what is probably China’s worst air disaster in more than a decade. Experts have said it is unlikely that anyone survived the crash.
On Thursday, rescuers said they had found engine components, part of a wing and other “important debris” as they searched the mountainside in a rural part of the Guangxi region for a fourth day.
A four-foot-long piece of debris suspected to be from the plane was found more than six miles from the main crash site, said Zheng Xi, the commander in chief of the Guangxi Fire Rescue Corps. As a result, search teams will widen the area they are combing, he added.
At the main crash site, a state broadcaster showed the workers digging with shovels around a large piece of wreckage that the reporter described as a wing, which bore part of the China Eastern logo and was perched on a steep, barren slope fringed by dense thickets of now-flattened bamboo. Heavy rains had left the roads slick and inundated the earth with muddy pools.
A day earlier, the workers had found a black box, believed to be the cockpit voice recorder, which could provide investigators with crucial details. Officials said it was damaged but that its memory unit was relatively intact. The plane’s second black box, which records flight data, has yet to be recovered.
China Eastern officials have described the crew as having no health problems or faults on their records. Their past performance was “very good,” Sun Shiying, the chairman of China Eastern Airlines’ Yunnan branch, said on Wednesday. When reached by phone, an airline representative declined to answer further questions about the crew.
China Eastern did not identify the crew by name, but the state-owned Ta Kung Pao newspaper and Phoenix Magazine in Hong Kong identified the pilot as Yang Hongda and the first co-pilot as Zhang Zhengping.
Mr. Zhang, who was born in 1963, was one of China’s most experienced pilots, having taken up flying as a teenager in Yunnan Province in the early 1980s, according to a 2018 profile by CAAC News, the Civil Aviation Administration of China’s newspaper. He was selected from among thousands who applied to aviation school. There, he trained on a copy of a Soviet-model biplane. Later, after joining China Yunnan Airlines, he flew Antonov An-24s, a turboprop model once common in Chinese commercial aviation, according to the article.
After China Yunnan purchased its first Boeing models, Mr. Zhang traveled to Seattle in 1988 to train on the Boeing 737-300, the newspaper said. He later learned to fly the Boeing 767, a wide-body aircraft. Over his career as a commercial pilot with China Yunnan, which later merged with China Eastern, Mr. Zhang flew four different models of aircraft and accumulated 31,769 hours of flight experience.
“At China Eastern Airlines Yunnan company, he is one of the few veteran pilots, a mentor to young captains, and a witness to the rapid growth of Yunnan’s aviation industry since the era of reform and opening up began 40 years ago,” the newspaper said, referring to the market reforms begun in China after the Mao era.
The airline commonly paired young pilots with older pilots, and Mr. Zhang had mentored more than 100, CAAC News said. Mr. Yang was one of them.
Mr. Yang, the son of a China Eastern pilot, had steadily progressed up the ranks at the airline, Phoenix Magazine said. He had begun flying 737s in 2018, the airline said. He was 32 and had a daughter who had just celebrated her first birthday, the newspaper Southern Weekly, based in the city of Guangzhou, reported.
In addition to Mr. Zhang and Mr. Yang, a second co-pilot with 556 hours of experience was also on the flight. The three had valid health certificates and met all other requirements to fly, the airline said. Their “family conditions were stable,” Mr. Sun said.
Experts said that investigating the crash, which involved a sudden dive from cruising altitude in good weather, would require a close look at both the aircraft and the pilots, including the possibility that the plane was deliberately brought down. But they stressed that the cause was far from determined.
“Certainly an intentional downing is always a part of any investigation, and especially with this particular flight profile,” said Hassan Shahidi, chief executive of the Flight Safety Foundation, a nonprofit organization created after World War II to promote aviation safety. But he cautioned that it was “premature to jump onto any possibilities.”
Steven C. Marks, a Miami lawyer who specializes in lawsuits against Boeing and Airbus that allege equipment failures, said he was skeptical that a pilot had intentionally caused the crash, particularly given the likelihood that others would have intervened.
“If the captain were intending to commit suicide, they’d have to overcome the other flight crew members,” Mr. Marks said.
Liu Yi, Li You and John Liu contributed research.