Two U.S. officials briefed on the matter said the assessment, which was not intended for public release, was prepared months ago and was solely based on available satellite and other evidence, and not based on more detailed findings by investigators. Another government official said the assessment is the most current view of U.S. officials based on what is known so far about the plane's fate.
The intelligence assessment falls short of establishing any firm conclusions of what happened to MH370. But it could renew focus on the two pilots, or perhaps someone else, in the aircraft's cockpit. CNN reported earlier this year
that U.S. intelligence was leaning towards deliberate acts being behind the plane's erratic flight, but not that intelligence had reached a conclusion.
The FBI and NTSB provided assistance to Malaysian investigators leading the the probe into the airliner's disappearance. The airliner's crew has been the focus of attention since the mysterious disappearance, but no proof has emerged indicating they intended to destroy the plane. Law enforcement and intelligence agencies from numerous countries examined the plane's manifest of crew and passengers and found no significant information to suggest anyone on board posed an obvious threat.
Spokesmen for the FBI and Director of National Intelligence declined comment.
French investigators are expected to examine the piece of aircraft debris found in recent days near the French Indian Ocean island of Reunion to determine whether it belongs to MH370. If it does, investigators are expected to examine the aircraft part for any signs that point to an explosion or catastrophic failure. However, it's likely that establishing a cause for the disaster will have to wait for more of the wreckage to be found and, more crucially, the data recorders believed to be underwater somewhere.
A report earlier this year from Malaysian investigators found no indications of unusual behavior among the pilots and cabin crew of Flight 370 before it took off and vanished in the early hours of March 8, 2014.
"There were no behavioral signs of social isolation, change in habits or interest, self-neglect, drug or alcohol abuse of the captain, first officer and the cabin crew," the report said.
The U.S. intelligence assessment was largely focused on the multiple course changes the aircraft made after it deviated from its scheduled Kuala Lumpur to Beijing route. Analysts determined that, absent any other evidence, it's most likely someone in the cockpit deliberately moved the aircraft to specific waypoints, crossing Indonesian territory and eventually toward the south Indian Ocean.
The Malaysian report said the aircraft was seen on Thai and Indonesian radar, as well as Inmarsat regional satellite for hours after it veered off course. "The analysis showed the aircraft changed course shortly after it passed the northern tip of Sumatra (Indonesia) and travelled in a southerly direction until it ran out of fuel in the southern Indian Ocean west of Australia," the report said.
The Malaysian investigative report said MH370's captain, Zaharie Ahmad Shah, didn't have any personal or financial problems that would cast suspicion on him.
"The captain's ability to handle stress at work and home was good. There was no known history of apathy, anxiety, or irritability," the report said. "There were no significant changes in his lifestyle, interpersonal conflict or family stresses."
Investigators looked into the backgrounds of the different crew members. They also examined closed-circuit TV footage of the flight crew at airports on at least three previous flights and saw no signs of change in behavior.
Malaysia Airlines Chief Executive Ahmad Jauhari Yahya has vehemently defended his employees. "We do not suspect any one of our crew until there's such evidence," he said.
Malaysian investigators also said they couldn't rule out any other possible causes for the aircraft's demise.