A Queensland couple who wanted to spend more time travelling in their older age were two of the six Australian passengers on board a missing Malayasia Airlines flight.
The Boeing 777 aircraft, carrying 239 people, vanished while flying across the ocean between Malaysia and Vietnam early Saturday morning.
Neighbours said Catherine and Robert Lawton, aged 53 and 57, had already been on a trip to Asia and were ''looking to see a bit of the world'' now their three daughters had moved out.
Springfield Lakes resident Robbie Daintith, who lives across the road from the couple and would often put their bins out when they travelled, said they were ''lovely people'' who adored their young grandchildren.
''We knew from talking to them that they were planning to go away for a period of time again. They did a similar trip this time last year,'' Mr Daintith said.
''They were lovely people who always said hello, were always happy to have a chat and always offering to help out in anyway they could.''
He said Ms Lawton didn't work because of a visual impairment but her husband was employed.
The pair is understood to have been travelling on the flight with Brisbane couple Rodney and Mary Burrows.
Two other Australians on board the flight have been identified as Yuan Li, 32, and Naijun Gu, 31.
The Australian government has released a statement saying it holds "grave fears" for the Australian passengers.
Department of Foreign Affairs and Trade spokeswoman Kerin Ayyalaraju said Australian consular officials were in "urgent and ongoing contact" with Malaysia Airlines, and were speaking with distraught family members in Australia and offering "all possible consular assistance".
The plane vanished somewhere off Vietnam's Tho Chu Island, northwest off the country's southernmost Cape Ca Mau. The airline lost contact with the aircraft after it departed Kuala Lumpur.
It was expected to land in Beijing at 6:30am carrying 239 people, including two infants and 12 crew members.
Passengers included 152 Chinese people, 38 Malaysians, 12 Indonesians, three Americans and two Canadians. There were also passengers from New Zealand, Italy, France, Ukraine, Russia, Netherlands, Austria and Taiwan.
If all passengers are found dead, it will be the world's worst air tragedy in a decade.
The aircraft's pilot was Zaharie Ahmad Shah, a 53-year-old Malaysian captain, who has flown more than 18,000 hours. The first officer was Fariq Ab Hamid, 27, also of Malaysia, who has flown more than 2700 hours.
Malaysia Airlines initially reported seven Australians were on board, but the number was quickly revised to six.
The airline said it had been successful in contacting about 80 per cent of family of passengers.
Vietnam's official website said the plane disappeared in Vietnam's airspace.
"The plane lost contact in Ca Mau province airspace before it had entered contact with Ho Chi Minh City air traffic control," a statement posted on the website said.
Conflicting reports surfaced on Saturday afternoon over claims in Vietnamese and Chinese media that the missing plane's signal had been detected in the middle of the ocean.
Vienamese news site VN Express had quoted Pham The Hien, director of the country's search and rescue co-ordination centre, saying a signal was detected 230 kilometres south-west of Cape Ca Mau. But he later said those reports had been inaccurate, and his team was continuing to look for the missing plane's signal.
With the arrivals board at Beijing's international airport still showing the Malaysian Airlines flight as delayed, distraught family members were being shepherded by police and airport staff to a nearby hotel to await further information.
One woman, Zhai Le, said her friend was on board the flight.
"They keep saying there's no information," she said through tears.
Another man, who declined to be named, said he had been waiting for his boss, a French national, when he heard the news.
Malaysia Airlines said in a statement that it was working with the authorities who have activated their search and rescue team to locate the aircraft.
An unconfirmed report from a flight tracking website said the plane had plunged more than 200 metres and changed course in the last minute that it had transmitted data.
Chinese authorities have reportedly said the flight never entered Chinese airspace.
"It doesn't sound very good," retired American Airlines captain Jim Tilmon told CNN on Saturday.
He said that the route was mostly overland, which meant that there would be plenty of radars and radios to contact the plane.
"I've been trying to come up with every scenario that I could just to explain this, but I haven't been very successful."
He said the plane was "about as sophisticated as any commercial airplane could possibly be".
Malaysia Airlines denied reports circulating on the internet the plane had landed safely in Nanjing China.
Fuad Sharuji, from the airline's operation control centre, confirmed contact was lost two hours into its six-hour flight. The pilots made no distress call.
The missing plane is believed to have been involved in a crash in August, 2012, when it damaged the tail of a China Eastern Airlines plane at Shanghai Pudong Airport, according to unconfirmed reports.
In the incident, the tip of the wing of the Malaysia Airlines Boeing 777 broke off.
Malaysia Airlines said its "thoughts and prayers" were with all the passengers on board the missing plane, and their families.
"[The] focus of the airline is to work with the emergency responders and authorities and mobilise its full support," chief executive Ahmad Jauhari Yahya said.
Malaysia Airlines is the national carrier of Malaysia and one of Asia's largest, flying nearly 37,000 passengers daily to some 80 destinations worldwide.
The airline said the public can call +60-378841234 for information about the plane.
There were no storms in the area of the South China Sea where the plane was flying across. The weather was generally fine with light clouds.
Malaysia Airlines' vice president of operations told CNN that no distress call or problems were reported from the aircraft prior to its disappearance. The plane was reportedly flying at 35,000 feet at the time.
Malaysia and Vietnam were conducting a joint search and rescue, Malaysia Airlines chief executive Ahmad Jauhari Yahya said, but gave no details. China has also sent two maritime rescue ships to the South China Sea to help in any rescue, state television said on one of its microblogs.
"We are extremely worried," Chinese Foreign Minister Wang Yi told reporters in Beijing. "The news is very disturbing. We hope everyone on the plane is safe."
The plane had enough fuel to fly for seven hours, one hour more than the flight time to Beijing.
Heart-wrenching airport scenes
Beijing: As it became apparent this was not a routine plane delay, heart-wrenching scenes unfolded at the arrivals hall at Beijing's international airport terminal.
With the arrivals board still showing the Malaysian Airlines flight MH370 from Kuala Lumpur as delayed on Saturday morning, distraught family members and friends broke down as news filtered through that the flight had in fact gone missing hours earlier.
"They keep saying there's no information," Zhai Le told Fairfax Media, explaining through tears that she had a friend on board the flight.
One woman was seen crouched down on the floor sobbing, before a male companion and police led her away. Another man appeared shell-shocked as he explained he had been waiting to pick up his boss, a French national, when he heard the news.
Chang Ken Fei, a Malaysian waiting at Beijing airport for friends to arrive, said: " At first I thought the plane was just delayed as normal, so I came a bit later, I've just been waiting and waiting," he told Reuters.
Police and airport staff escorted relatives to the Beijing Lido Hotel to wait for news, even as flustered family members continued to arrive at the airport, desperate for information.
With 154 Chinese nationals on the Malaysian Airlines flight, the news has received blanket coverage in China, and Chinese foreign minister Wang Yi cut short a scheduled press briefing at the National People's Congress to attend to the fall-out.
"We are extremely worried," Mr Wang said. "We are doing all we can to get details. The news is very disturbing."
China's state-run news agency Xinhua reported the plane was lost in airspace controlled by Vietnam, and did not make contact with Chinese air traffic controllers. Chinese authorities dispatched two rescue boats two assist with the search and rescue operations and said there were no storms in the area of the South China Sea where the plane was flying across.
At the Lido on Saturday afternoon, a steady stream of visibly upset relatives, some with heads bowed, arrived fearing the worst, running a gauntlet of reporters before entering a room under police guard.
"I know nothing, I really don't have anything to say," one man whispered through a crush of reporters, squeezing the hand of an elderly man trailing behind him.
smh.com.au, with Philip Wen and agencies