The Civil Aviation Administration of China (CAAC), in an initial briefing on the loss of the China Eastern Boeing 737-800 (B-1791), says air traffic controllers monitoring traffic in the Guangzhou flight information region saw the aircraft enter a steep descent and attempted to make contact, but “received no reply”.

Flight MU5735 was just over an hour into its journey from Kunming to Guangzhou at 29,000ft when the fatal descent began.

At present, says the CAAC, investigators are searching for the flight data recorder and cockpit voice recorder. The aircraft hit the ground at high speed and wreckage is widely spread. As a precaution the agency has declared all China’s 737s grounded for checks, although it has not been specific about what checks may be required, and a safety review of aviation infrastructure like ATC and maintenance organisations has been ordered.

China is proud of its safety record, and had not seen an airline fatal accident on its territory since August 2010 when a Henan Airlines Embraer EMB190 crashed on approach to land in fog at Yinchun Lindu airport.