Aviation experts say there are two possible causes of the disappearance: mechanical error or human error on board, which could include an electrical outage, a fire, a hijacking or bomb, and many other reasons. There is no hard evidence one way or another at his point, they say.
The transponders on board the plane that transmit signal's about the plane's location were somehow disabled or turned off, according to authorities. Investigators are looking at how and why they transponders were not functioning.
Authorities have not ruled out terrorism but have found no evidence of it.
Malaysian government officials today played a recording of the pilot's last recorded words for passengers' family members. The air traffic control worker said to the pilot, "We have to hand you over to Ho Chi Minh City," to which the pilot replied, "All right, goodnight."
Four passengers who were waiting on the stand-by list to board flight MH370 were given seats on the plane after four ticketed passengers did not show up for the flight.
239 people were on board the flight, made up of 227 passengers (including one infant and one toddler) and 12 crew members.
Three Americans, including two children, are among the missing. Philip Wood, 50, an IBM executive, had just come from Texas where he was visiting family on his way to Beijing.
Fourteen nationalities were on board, though 152 passengers were Chinese.
Twenty passengers on the plane worked for the Austin, Texas, company Freescale Semiconductor. Another passenger, Chng Mei Ling, worked as an engineer for the Pennsylvania company Flexsys America LP.
Pilot Zahari Ahmad Shah, 53, was a veteran pilot who joined Malaysia Airlines in 1981 and had over 18,000 flying hours.
Fake Passports Used By Two Passengers
Investigators discovered that two passengers used stolen passports, one from Austria and one from Italy, to board the flight.
Interpol identified the two as Iranians Seyed Mohammad Reza Delavar, 29, and Pouria Nourmohammadi, 18, and said they have no known links to militant groups, downplaying the possibility they were terrorists.