A New Zealand oil rig worker has claimed to have seen the missing Malaysian Airlines plane burning in the sky.
Read more: Debris found at sea - reports
Mike McKay told his employers, in an email made public overnight, that he had observed the plane burning at high altitude.
"I believe I saw the Malaysian Airlines plane come down. The timing is right," he said.
"I tried to contact the Malaysian and Vietnam officials several days ago. But I do not know if the message has been received."
Mr McKay said he was on the oil rig Songa Mercur, off south east Vietnam.
When he observed the plane it appeared to be in one piece, he said.
"From when I first saw the burning (plane) until the flames went out (still at high altitude) was 10 to 15 seconds," he wrote.
ABC reported that Vietnam officials confirmed they had received the email but found no wreckage in the area specified.
Final words: All right, good night
The last words heard five days ago from the missing Malaysia Airlines plane were "all right, good night".
Aviation officials said the words came from the cockpit of Flight MH370 and were made in response to Malaysian air traffic controllers who told the flight crew that they were entering Vietnamese airspace and that air traffic controllers from Ho Chi Minh city were taking over.
The brief phrase was revealed at a two-hour meeting in Beijing yesterday between the Malaysian Government and nearly 400 relatives of missing Chinese passengers. Nothing has been seen of the aircraft, which was carrying 239 passengers and crew, including 153 Chinese nationals, since last Saturday despite a massive international air, sea and land search.
Malaysian officials went to Beijing partly because tensions have been rising in China over Kuala Lumpur's often confused handling of the search, and contradictory information released by authorities.
The packed meeting, fronted by Malaysia's envoy to China, Datuk Iskandar Sarudin, was live-tweeted by Singapore's Straits Times newspaper.
In one confusing exchange, an official, pressed by relatives if military radar had picked up the plane, replied the Malaysian military was assisting investigations "at a high level".
Asked repeatedly what information the military had given authorities, he finally replied that "now is not the time" to reveal it.
The question reflected a switch by Malaysia in the focus of the aircraft search to the Andaman Sea north of the Strait of Malacca.
That shift follows claims that the country's air force detected a signal suggesting the missing plane had veered massively off course, returning west across the Malaysian mainland instead of heading northeast towards Beijing, its destination.
Rodzali Daud, the head of the Malaysian air force, was quoted as saying the plane had been detected in the northern part of the Strait of Malacca at 2.40am on Saturday.
"After that, the signal from the plane was lost," he said, according to the Berita Harian newspaper.
Malaysia's air force added to the confusion yesterday by rejecting those claims as "inaccurate and incorrect".
"All ongoing search operations are at the moment being conducted to cover all possible areas where the aircraft could have gone down in order to ensure no possibility is overlooked," it said in a statement.
It would be inappropriate to issue "official conclusions as to the aircraft's flight path until a high amount of certainty and verification is achieved", the statement added.
However, a military source hinted authorities were now convinced the plane had flown back over Malaysia. "[The plane] made it into the Malacca Strait," the source told Reuters.
Zhang Qihuai, the vice-chairman of the Beijing-based Aviation Law Society, said the only certainty was that the plane had suffered some kind of "sudden occurrence". He criticised the pace of the Malaysian response.
"Emergency action should have been taken immediately after this sudden occurrence. If the Malaysians had deployed planes to search for the missing flight the minute the flight was found to be out of contact, it might have saved a lot of time and effort," he said.
Malaysian police chief Khalid Abu Bakar, who has been ordered to look at possible criminal aspects in the disappearance of Flight MH370, said hijacking, sabotage and issues related to the pilots' psychological health were all being considered.
An Australian TV station reported that the first officer on the missing plane, Fariq Abdul Hamid, had invited two women into the cockpit during a flight two years ago. One of the women, Jonti Roos, described the encounter on Australia's A Current Affair.
Roos said she and a friend were allowed to stay in the cockpit during the entire one-hour flight on December 14, 2011, from Phuket, Thailand, to Kuala Lumpur. She said the arrangement did not seem unusual to the plane's crew.
"Throughout the entire flight, they were talking to us and they were actually smoking throughout the flight," said Roos.
Malaysia Airlines said it took the allegations, which it said it was not able to confirm, very seriously, adding: "We are in the midst of a crisis and we do not want our attention to be diverted."
Meanwhile, aviation experts around the world continued to puzzle over how the plane could simply have disappeared.
"There are two black box recorders, a cockpit voice recorder and a data recorder and each is supposed to send a signal. I cannot think why they might not be sending that signal unless the nose of the plane hit the water with such force they were destroyed," one told the Telegraph.
A Malaysian search and rescue expert said finding the missing plane would take time. "The ocean is vast and deep," he said.
Boeing 777 weak spot warning
American transport officials warned of a potential weak spot in Boeing 777s which could lead to the "loss of structural integrity of the aircraft" four months before the disappearance of Malaysia Airlines Flight MH370.
The Federal Aviation Administration in Washington drew up an Airworthiness Directive in November. It was triggered by reports of cracking in the fuselage skin underneath a Boeing aircraft's satellite antennae.
In its directive, the FAA, which is responsible for supervising the safety of American-made aircraft such as Boeing, told airlines to look out for corrosion under the fuselage skin.
This, the FAA said, could lead to a situation where the fuselage was compromised leading to possible rapid decompression, as well as the plane breaking up.
"We received a report of cracking and corrosion in the fuselage skin underneath the SATCOM antenna adapter," the FAA said. "During a maintenance planning data inspection, one operator reported a 16-inch (40cm) crack under the three-bay SATCOM antenna adapter plate in the crown skin of the fuselage on an aeroplane that was 14 years old with approximately 14,000 total flight cycles.
"Subsequent to this crack finding, the same operator inspected 42 other aeroplanes that are between 6 and 16 years old and found some local corrosion, but no other cracking. Cracking and corrosion in the fuselage skin, if not corrected, could lead to rapid decompression and loss of structural integrity of the aeroplane."
The FAA directive in November called for additional checks to be incorporated into the routine maintenance schedule of the worldwide 777 Boeing fleet.
According to a Malaysia Airlines spokesman, the missing aircraft was serviced on February 23, with further maintenance scheduled for June 19.