BEIJING/WASHINGTON (Reuters) - China's aviation regulator said on Monday that investigators were still looking into the cause of the crash of China Eastern Airlines Flight MU5735, almost a year after the plane came down, killing all 132 people on board.
The Boeing 737-800 crashed into a mountainous region in the southwestern Guangxi region on March 21, 2022, in China's deadliest aviation disaster in 28 years.
On the eve of the anniversary, the Civil Aviation Administration of China (CAAC) issued a three-paragraph statement that provided little detailed information and no data from the plane's so-called "black boxes" that would offer clues into its sudden plunge from cruising altitude.
"Because the accident is very complicated and extremely rare, the investigation is carrying on in an in-depth manner," the CAAC said, adding that experts had inspected more than 100 pieces of wreckage.
"Following on this, the technical investigation team will continue to carry out work such as cause analysis, experiments and verification, and will release relevant information in a timely manner according to the investigation's progress."
International Civil Aviation Organization rules require countries probing plane crashes to make a final report publicly available within 12 months or if that is not possible, to publish an interim statement on each anniversary, detailing the progress of the investigation and any safety issues identified.
But Greg Waldron, Asia managing editor of industry publication FlightGlobal said the brevity of the CAAC's one-year statement was unusual, noting that one-year reports published by other Asian countries were often dozens to hundreds of pages long and included detailed analysis.
"The objective is not to attribute blame, but rather to improve the safety standards of the industry in general," he said.
While the MU5735 tragedy like all aircraft disasters was complex, the cockpit voice recorder and flight data recorder of the aircraft were recovered days after the crash, he added.
"This data from this equipment should have yielded detailed insights into conditions with the aircraft and in the cockpit at the time of the crash."
The Chinese regulator said investigations so far had focused on how key components were performing before the crash, and looked into air traffic control, the passengers and what the plane was carrying.
Investigators looking into the crash were examining the actions of the crew on the flight deck with no evidence found of a technical malfunction, two people briefed on the matter told Reuters in May 2022.
In a response to internet rumours of a deliberate crash, the CAAC said at the time the speculation had "gravely misled the public" and "interfered with the accident investigation work."
A final report into the causes of the crash could take two years or more to compile, Chinese officials said last year.
Boeing declined to comment and China Eastern did not immediately respond to a request for comment.
A summary of a preliminary report issued last year before the jet's black boxes were analysed gave no indication of the focus of the investigation. It noted the crew were qualified, the jet was properly maintained, the weather was fine and no dangerous goods were onboard.
The cockpit voice recorder and flight data recorder were sent to a U.S. National Transportation Safety Board (NTSB) laboratory in Washington, a move Beijing had supported despite rising political tensions between the two countries. NTSB investigators also travelled to China.
The NTSB said on Monday it continued to support the Chinese-led investigation.
NTSB Chair Jennifer Homendy said last week the agency has had a "really good working relationship with China" during the investigation. "Our investigators went to China. We got what we needed," Homendy said.
The 737-800 is a widely flown predecessor to Boeing's 737 MAX and has been in service since 1997 with a strong safety record.