According to CCTV news, on January 5th, an embedded emergency door of a Boeing 737 MAX 9 aircraft in the United States fell off. The National Transportation Safety Board of the United States stated that the bolt that played a crucial role in fixing the door plug was not installed when the aircraft left the factory. On March 13th, the Chairman of the National Transportation Safety Committee of the United States wrote to the Senate Commerce Committee, stating that Boeing was unable to provide the key footage and documents required for the investigation, which increased the difficulty of the accident investigation.
On the 13th, Jennifer Hormendy, Chairman of the National Transportation Safety Commission, wrote to the Senate Commerce Committee stating that they still do not know who is responsible for the opening, closing, and installation of the doors on the malfunctioning aircraft. The committee has been requesting Boeing to provide maintenance surveillance footage of the aircraft before takeoff, but Boeing claims that the footage has been overwritten. Homendi also stated that Boeing stated that they were unable to find records of the accident aircraft maintenance personnel, and the lack of these records would complicate the investigation.