The Civil Aviation Administration of China (CAAC) issued a preliminary report on Wednesday regarding the China Eastern Flight MU5735 crash.

The black boxes were severely damaged and data retrieval is underway, according to the report.

The aircraft took off from Runway 21 of Kunming Changshui International Airport at 13:16 Beijing time, rose to 8,900 meters high at 13:27, and entered Guangzhou control area along A599 route at 14:17, the report said.

At 14:20:55, the radar of Guangzhou regional control raised an alarm of "altitude deviation." The controller immediately called the MU5735 crew but no reply was received.

At 14:21:40, the radar recorded the last piece of information of the aircraft at the standard barometric altitude of 3,380 meters, with a ground velocity of 1,010 km/h and a heading of 117 degrees. Then the radar signal disappeared.

Before deviating from its cruising altitude, no abnormalities were reported. The last normal air-to-ground call was at 14:16, according to the report.

There was no fault report before its flight, and no dangerous goods were declared onboard.

The flight's crew met relevant qualifications for executing their flying mission, the report said.

Flight MU5735 crashed with 123 passengers and nine crew members aboard into a mountain in the Guangxi Zhuang autonomous region at 2:21 pm on March 21.