This is the last 54 minutes of cockpit communication aboard the missing Malaysia Airlines flight MH370.

A transcript of conversations between the co-pilot and the control tower, and later with air traffic control, runs from the time the Boeing 777 airliner was taxiing on the runway to its last known position thousands of feet above the Gulf of Thailand.

It includes communications when the plane is believed by investigators to have already been sabotaged and the last words of Fariq Abdul Hamid, the 27-year-old co-pilot: “All right, good night”.

Last night analysts said the sequence of messages appeared to be “perfectly routine”.

However two features, they said, stand out as potentially odd.

The first was a message delivered by the cockpit at 1.07am, saying that the plane was flying at a cruising altitude of 35,000 feet. This message was unnecessary as it repeated a call that had already been delivered six minutes earlier.

But this message occurred at a crucial moment in the plane’s flight history: it was at 1.07am that the plane’s ACARS signalling device sent its last message before being disabled during the next 30 minutes, apparently deliberately. A transponder signalling device was disabled at 1.21am but investigators believe the ACARS was shut down before Hamid’s final farewell message.

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 subsequent sharp turn westward occurred during the handover from air traffic controllers in Kuala Lumpur to those in Ho Chi Minh City.

“If I was going to steal the aeroplane, that would be the point I would do it,” said Stephen Buzdygan, a former British Airways pilot who piloted Boeing 777s.

“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.”

The fresh details of the communications add to the speculation over of the fate of MH370 – whether it was the victim of a sudden accident or a hijacking; the transcript also suggests that if the pilots were involved in a plot they were very careful to hide their true intentions.

Last night, dozens of ships and aircraft were still involved in a painstaking search of an area off the Australian coast where debris potentially from MH370 was spotted by a spy satellite earlier this week.

Malaysia has begun appealing to the handful of nations with deep sea detection equipment for help in what may be a long search for the aircraft’s black box. The area of interest spans 9,000 square miles across waters that are up to 13,000 feet deep.

Warren Truss, Australia’s deputy prime minister, acknowledged that the apparent debris may now never be found because of the area’s deep waters and strong currents.

“Something that was floating on the sea that long ago may no longer be floating,” he said. “ It’s also certain that any debris or other material would have moved a significant distance over that time, potentially hundreds of kilometres.”

Hishammuddin Hussein, Malaysia’s acting transport minister, said the search was proving frustrating and cautioned that “this is going to be a long haul”.

“We have to trench down and the focus is to reduce the area of search and possible rescue,” he said.

Malaysia Airlines revealed yesterday that the aircraft was carrying some lithium ion batteries, which are deemed “dangerous” cargo and can overheat and cause fires. But Ahmad Jauhari Yahya, the airlines head, said the batteries – used in laptops and mobile phones – were packed and carried in accordance with regulations and were unlikely to have posed a threat.

Mr Ahmad Jauhari has previously revealed that Hamid, the co-pilot, spoke the final message on the plane but yesterday would not comment on whether he appeared to be under duress.

According to the cockpit transcripts, from the moment of 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.”

Steve Landells, a former British Airways pilot who flew Boeing 777s, gave his assessment of the aparent anomoly of the repeated messages from plane when setlign at 35,000. He said a 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.”