This was according to a recording captured on the military radar, said RMAF chief General Tan Sri Rozali Daud.
He described an air turn back as a flight which had deviated from the flight path and into a reciprocal heading.
"We are also baffled by the no signal from the ELT (emergency locator transmitter) emergency beacon.
"What we have done is to look into the recording on the radar that we have and we realised that there is a possibility that the aircraft had made a turnback.
"At this juncture, we are still trying to collaborate with the civil radar and other international agencies, and with this collaboration, we hope we can get a better picture," Rozali told a press conference Sunday.
MAS group chief executive officer Ahmad Jauhari Yahya said an air turn back could be launched when a pilot is unable to proceed on the planned flight path.
"Normally, he (the pilot) makes the decision to turn back but he will report to the base and also to the ATC (air traffic control centre).
"From what we know, from both the ATC recordings as well as our own (the base), there was no such distress signal or distress call.
"So, we are equally puzzled as well," Ahmad Jauhari said.
Department of Civil Aviation director-general Datuk Azharuddin Abdul Rahman declined to answer when asked if it was possible for a Boeing 777 to turn off all its diagnostic information and disappear from the radar during a flight.
"That is something that all of us would like to know the answers to and we are investigating that matter.
"We are talking to the experts from the airline (industry) and we will get assistance from Boeing.
"That will be part of the investigation. I just cannot speculate something that we are not sure of. It is better that we get (the information) from the right sources (on) the technical issues of the aircraft," Azharuddin said.
The new possibility of an air turn back has prompted the authorities to widen the scope of its search and rescue.
Armed Forces chief General Tan Sri Zulkefli Mat Zain said the number of assets deployed for the mission as at Sunday included 22 aircrafts, 40 vessels, and one helicopter.
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