The Vietnamese government reported today that air force pilots spotted large oil slicks off the country's southern coast, according to The Associated Press. There was no confirmation that the slicks were related to the missing plane, but the statement said the slicks were consistent with the kinds expected to be left by a crashed jetliner.
China has dispatched two maritime rescue ships and the Philippines deployed three air force planes and three navy patrol ships to help. The Navy's USS Pinckney is also on its way to help the search effort, the 7th Fleet announced on Twitter this morning.
Flight MH370 departed Kuala Lumpur at 12:55 a.m. local time Saturday, and was scheduled to land in Beijing at 6:30 a.m., the airline said. It went missing two hours into the flight and disappeared off the radar.
The plane's route would take the aircraft from Malaysia across to Vietnam and China. Vietnam said on its official website that its air traffic controllers lost contact with the plane "in Ca Mau province airspace before it had entered contact with Ho Chi Minh City air traffic control." Ca Mau is near the southern tip of Vietnam.
The plane was meant to transfer to Ho Chi Minh City air traffic control at 1722 GMT but never appeared, the statement said, citing a senior Ministry of Defense official.
Malaysia's defense minister told a news conference, "We are trying to do everything in our power to [determine] where the plane is."
Malaysia Airlines said the captain of the airliner, Zaharie Ahmad Shah, was an experienced 53-year-old pilot who had 18,365 hours of flying since joining the airline in 1981. The first officer on the flight was identified as Fariq Hamid, 27, and had about 2,800 flight hours since 2007.
Meanwhile, the flight information board at the airport in Beijing indicated the flight was delayed.
An airport official wrote on a white board near the arrivals customer service desk that families of the missing passengers should go to the Lido Hotel. The notice was put up about four hours after the plane was overdue.
"Friends and families should go to the Lido Hotel for more information," Eric Yangchao, customer service representative for Beijing International Airport, told ABC News. Family members took a shuttle bus to the hotel.
In a statement on Twitter, Boeing said it was watching the situation closely. The Malaysian aircraft, a Boeing 777-200, is 11 years and 10 months old. The 777 model had not had a fatal crash in its 20-year history until the Asiana crash in San Francisco in July 2013.
ABC News' and Joohee Cho contributed to this report.