It is arguably the biggest mystery in aviation history: What happened to  Flight MH370?

Malaysia is releasing a long-awaited report into the disappearance of the Malaysia Airlines plane, which vanished with 239 aboard en route to Beijing from Kuala Lumpur on March 8, 2014.

Relatives of people aboard the flight, who were given the official investigation team’s report on Monday morning at the Malaysian transport ministry, said they hoped it might give them answers.

However, the report, which was due to be released publicly in the afternoon, was unlikely to reveal definitive conclusions about that fateful day four years ago.

Here is everything we know – and don’t know – about the unexplained tragedy….