Malaysia's transport minister vowed on Thursday to take stern action against an air traffic control supervisor if it is confirmed that he was asleep on the job when Malaysia Airlines Flight MH370 disappeared a year ago.

An interim investigation report last Sunday contained transcripts of conversations between air traffic controllers in the region and the airline that revealed confusion in the hours after the Boeing 777 dropped off radar with 239 people aboard while flying from Kuala Lumpur to Beijing.

In one conversation four hours after the plane disappeared, a Kuala Lumpur air traffic controller told a Malaysia Airlines official that he would need to wake up his supervisor when pressed on the exact time of the last contact with the plane. The controller came on duty after the plane vanished.