Malaysia Airlines Flight MH370 took off from Kuala Lumpur heading toward Beijing on the morning of March 8, but lost contact with air traffic control an hour later and disappeared off the radar.
No trace of the plane and the 239 people on board have been found and few details about what could have happened to the plane have been released.
Here's what we know now as of now about the investigation into missing flight MH370.
"Indications" Send Searchers into Indian Ocean
The U.S. moved the USS Kidd into an area where the Indian Ocean and the Andaman Sea merge because there are "indications" the plane may have crashed into the water there, a senior official told ABC News. That is hundreds of miles to the west of flight MH370's flight path, which was northeast towards Beijing.
The Pentagon official said the U.S. didn't have detailed information about why they think it went into the Indian Ocean, but that it may have flown four to five hours after its last contact with radar and gone into the sea there.
Malaysian officials admit that the plane could have continued to fly for several hours after it dropped off the radar.
They dismissed as "inaccurate" a Wall Street Journal report that the plane's Rolls Royce engine sent signals after radar lost contact. The engines, which are designed to transmit bursts of data to ground during the flight, did not convey any meaningful data about the plane's location or disappearance, they said.
Malaysia, which continues to be the lead country investigating the disappearance, said that the last concrete data they have from the plane is a radar contact at 1:07 a.m. local time.
Chinese satellite images that were thought to show possible plane wreckage led to a search that came up empty.
The Search Expands:
The search has been expanded again, now into the Andaman Sea and the northern edge of the Indian Ocean.
Malaysia has asked India for help in searching for radar contacts with the plane and for searching for the plane.
More than 40 ships and 39 aircraft from 12 countries are scanning the Straits of Malacca, the Andaman Sea and the South China Sea for signs of the plane but have not found any debris yet.
The search has been broadened to encompass 27,000 square nautical miles, an area roughly the size of Indiana.
Flight MH370 departed Kuala Lumpur International Airport in Malaysia, headed for Beijing, China, around 12:41 a.m. local time on Saturday. It showed up on radar two minutes later.
The last reading from MH370's transponder was at 1:21 a.m. The last sighting of the plane on radar was at 1:30 a.m. At the time the plane was on its route over the South China Sea heading for the southern tip of Vietnam. An air traffic controller told the plane's captain he was
about to be handed over to air traffic control out of Ho Chi Minh City.
The pilot responded, "All right, good night." The pilot never made contact with air traffic control in Ho Chi Minh City.
Authorities have discovered that a flight showed up on the country's military defense radar at 2:15 a.m. local time in the Straits of Malacca, hundreds of miles due west of their last contact point and far from its route to Beijing. They said today that contact could possibly have been MH370.
The military radar also showed something make a turn back, meaning some aircraft reversing course, but they are not sure whether it was flight MH370. Because of the uncertain radar data, they are not sure of the plane's last position.
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.
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.