"We cannot determine with any certainty the reason the plane diverted from its planned route ... The team is unable to determine the real reason for the disappearance."
The report highlighted shortcomings in the Malaysian government's response that exacerbated the mystery.
It added that the "possibility of intervention by a third party cannot be excluded."
Families of passengers on board the missing flight MH370 said the report had no new findings on the reason for the plane's mysterious disappearance.
"It is so disappointing," said Intan Maizura Othman, whose husband was a flight steward on MH370.
"I am frustrated. There is nothing new in the report. Those who gave the briefing from the ministry of transport were not able to give answers as they were not [the ones] who wrote the report."
The Malaysia Airlines jet vanished with 239 people - mostly from China - on board, en route from Kuala Lumpur to Beijing.
No sign of it was found in a 120,000-square kilometre Indian Ocean search zone and the Australian-led hunt, the largest in aviation history, was suspended in January last year.
Earlier Monday, the wife of a man who died on board flight MH370 said she was angry the Malaysian government didn't offer to fly her from Australia for a briefing on the final report until the last minute.
Danica Weeks said an offer to fly her to the briefing from Queensland only came on Thursday, which was too little notice for a mother-of-two with a full-time job and pets.
"Unfortunately I'm not there today. A few of us, international families, have been unable to make it in that time frame so I'm very angry about that," Ms Weeks told AAP.