Safety Investigation Report 2018:2 Analysis/2.1 Diversion from Filed Flight Plan/2.1.2
SAFETY INVESTIGATION REPORT MH370 (9M-MRO)
2.1.2 Ho Chi Minh Air Traffic Services Operations
Based on the on-site interviews and briefing from the Team’s visit to the Office of the Vietnamese Civil Aviation Authority in Ho Chi Minh City, it was noted that the radar position symbol for MH370 dropped from the radar display at 1720:59 UTC (0120:59 MYT). MH370 had not reached waypoint BITOD which is 37 nm from waypoint IGARI and based on the aircraft speed of 480 kt, it would take approximately five minutes for MH370 to travel from IGARI to BITOD.
The Direct Line Coordination Communication transcripts between KL ACC and Ho Chi Minh ACC suggested that there were uncertainties on the position of the aircraft. This could come about from the level of understanding of the English language. The HCM Duty Controller also could not communicate effectively during the interviews and an interpreter was there to assist him.
Reference:
Ho Chi Minh radar data recording, page 33 to 41 and page 51 to 61 of the Direct Line Coordination Communication KL ACC Sector 3+5 Planner (Appendix 1.18G) transcripts between Kuala Lumpur ACC and Ho Chi Minh ACC).