On 13 March 2017, the crew of a Boeing 737-800 responded to an increase in indicated airspeed towards Vmo after changing the FMS mode during a high speed descent in a way that more abruptly disconnected the autopilot than they were anticipating which resulted in significant injuries to two of the cabin crew. The Investigation found that the operator s customary crew response to an overspeed risk at the airline concerned was undocumented in either airline or aircraft manufacturer procedures and had not been considered when an autopilot modification had been designed and implemented.