On the evening of March 22, the relevant personnel of the Civil Aviation Administration of China informed that the Boeing 737-800 passenger plane entered the Guangzhou control area at a cruising altitude of 8,900 meters at 14:17 on the 21st. At 14:20, the controller found that the aircraft altitude was sharp. Descended and called the crew several times, but received no reply.

At 14:23, the radar signal of flight MU5735 disappeared.

  What does "the controller called the crew several times but no response" revealed?

A civil aviation expert pointed out to The Paper that "it can't explain anything".

In his opinion, when the altitude drops sharply, the pilot should be too late to answer the controller's question because it is in a "crisis" moment.

  Regarding the possible cause of the accident, the above-mentioned civil aviation experts said that we did not have the on-site situation and original data, so we could not analyze and judge, and "we can't guess."

He said that when the black box is found, the sound of the cockpit can be restored, and now there is no need to jump to conclusions because the data available are very limited.

  Another expert in the civil aviation field also said that with limited information, it is too early to make a judgment.

  Qiao Shanxun, a member of the Chinese Aeronautical Society and who has published 2 aviation monographs, has systematically reviewed previous air crashes.

He mentioned that if the pilot issued a Pan-pan call sign in the air communication, it indicated that the aircraft was in an emergency, but at the time of communication, it was not serious enough to cause immediate danger to the life of the passenger plane itself or anyone.

This signal indicates a "quasi-emergency", which differs from "Mayday" (distress signal) in that the latter indicates a more urgent situation that could already cause aircraft damage or death at the time of the signal.

Sending a "Pan-pan" call sign means to notify other potential helpers (maybe specialized emergency aid agencies or other nearby flights) that there is an emergency, while issuing a "Mayday" is a call for help to all units that can be rescued to stop immediately All work, go to the rescue as quickly as possible.

  "If there is no call, it proves that the accident is extremely urgent, and the flight crew has no time or is unable to issue a distress signal, so from this detail we can feel that this matter is urgent." Qiao Shanxun said, "We can only say that based on the cases that have occurred in the past. Speculate about possible problems in the cockpit, but don't rule out situations that we haven't seen."

  On the evening of the 22nd, Zhu Tao, director of the Aviation Safety Office of the Civil Aviation Administration of China, reported that the aircraft in the accident was severely damaged and the investigation was very difficult.

In view of the fact that the investigation has just started, with the information currently available, it is still impossible to make a clear judgment on the cause of the accident.

In the next step, the investigation team will go all out to collect evidence from all parties, focusing on the search for the flight recorder at the scene of the accident, and carry out the analysis of the cause of the accident based on all aspects of information, so as to find out the cause of the accident in an in-depth and comprehensive manner. Announced immediately.

  Zhu Tao introduced that the emergency rescue work for the accident is still in progress, including the search for the two black boxes on the aircraft as soon as possible and data analysis to be carried out as soon as possible.

  As of the early morning of March 22, no survivors have been found in the on-site search and rescue of flight MU5735.

  The Paper reporter Zhong Yuhao intern Zheng Jiuzhou Zeng Wenpeng