Steve Landells, a former British Airways pilot who flew Boeing 777s, told The Telegraph that this second message was not required but he did not regard it as suspicious.
"It could be as simple as the pilot forgetting or not being sure that he had told air traffic controllers he had reached the altitude," he said. "He might be reconfirming he was at 350 [35,000 feet]. It is not unusual. I wouldn't read anything into it."
The other odd feature, which is one of the reasons for suspicions that the plane's disappearance was deliberate, was that its loss of communications and sharp turn westward occurred during the handover from air traffic controllers in Kuala Lumpur to those in Ho Chi Minh City.
Two minutes after the final message, the transponder was disabled.
"If I was going to steal the aeroplane, that would be the point I would do it," Stephen Buzdygan, a former British Airways pilot who flew Boeing 777s, told The Telegraph.
"There might be a bit of dead space between the air traffic controllers ... It was the only time during the flight they would maybe not have been able to be seen from the ground."
But the run of messages between MH370 and the ground involved routine calls between the cockpit and air traffic controllers and gives no hint of the drama that was to follow. It is believed Hamid, as co-pilot, was the sole communicator.
From his sign-in at 12.36 when the plane was still on the ground, Hamid, a 27-year-old flying enthusiast, gave routine accounts of the plane's location, ascent and altitude. Though he took a slightly casual approach and at times departed from formal wording, nothing in his banter gives any sign that the plane was about to fly off course and disappear.
"The communication up until the plane went to the changeover [to Vietnam] sounds totally normal," Mr Buzdygan said. "That kind of banter - I've done it hundreds of times. It is perfectly normal."
The Telegraph has repeatedly asked Malaysia Airlines, Malaysia's Civil Aviation Authority and the office of Malaysian prime minister Najib Razak to confirm the communications record; only the prime minister's office responded, saying it would not release this data.
Additional reporting by Adam Wu