It's been three days since Malaysia Airlines Flight 370 disappeared in the skies over the South China Sea about an hour into its route from Kuala Lumpur to Beijing.
Circulating speculation -- everything from mechanical failures to a terrorist attack -- has led to more questions than answers.
Among the latest updates, Malaysian authorities say two passengers on board travelling with stolen passports may have bought their ticket together, further raising suspicions they may have been connected to the plane's disappearance.
Here's more of what we know, and what we don't know about Flight 370 so far.
FACT: No physical signs of the plane
Malaysian authorities concluded Monday that the oil slick on the ocean's surface and small debris that were found near the last known location of the Boeing 777 was not connected to the plane.
“To confirm what happened that day on this ill-fated aircraft, we need hard evidence. We need concrete evidence. We need parts of the aircraft for us to analyze, for us to do forensic studies,” Azharuddin Abdul Rahman, director-general of Malaysia’s Department of Civil Aviation said at a press conference in Kuala Lumpur. “We are every hour, every minute, every second, looking at every inch of the sea.”
Investigators have widened their search. On Mar 8., Boeing, the maker of the plane, announced it was partnering with the US National Transportation Safety Board to join the search.
MYSTERY: An act of terrorism?
Shortly after reports circulated of the missing plane, a check into the passengers on board yielded that two male passengers had used stolen passports, prompting speculation that an act of terrorism may have contributed to the plane's disappearance. The passports were issued by Austria and Italy.
Although there haven't been any additional signs of terrorism, officials haven't ruled out the theory.
Officials said Monday they've isolated the two passengers in airport surveillance video.
"We confirmed now they are not Asian looking males," Rahman said at Monday's news conference.
When further probed, Rahman said one of the men is "black."
Other facts that have emerged in the investigation into the two suspicious passengers:
Thai police officials tracked down the purchaser of the tickets, according to CNN:
According to Thai police officials, an Iranian man by the name of Kazem Ali purchased the tickets for two friends who he said wanted to return home to Europe. While Ali made the initial booking by telephone, either Ali or someone acting on his behalf paid for the tickets in cash, according to police.
The owner of the Italian passport, Luigi Maraldi, said he reported in August that his passport was stolen.
FACT: No signs of distress
Malaysian authority suspect that whatever happened to the plane happened quickly. So quick, in fact that the pilots may not have had time to radio in any calls of distress. This information leads some aviation experts to suggest that perhaps the plane plummeted or exploded in mid-air. However, without debris, there's no saying that the plane crashed.
Despite the lack of a distress signal, radar data has shown that the plane may have turned around and headed back to Kuala Lumpur, according to CNN. This information has shifted the search to the Andaman Sea near the Thailand border.
FACT: Three Americans were on board
Of the 227 passengers on board, three -- two adults and an infant -- are American.