After a 15-month investigation, air crash investigators said a BUK missile fired from eastern Ukraine ripped through Malaysia Airlines flight MH17 last year, killing all 298 people on board.

The final report on the July 17, 2014, disaster was released by an international team led by the Dutch Safety Board.

Here are some of the key findings and recommendations:

Key findings

1. MH17 brought down by a warhead

The crash was caused by the detonation of a 9N314M-type warhead launched from the eastern part of Ukraine using a BUK missile system. The missile approached the plane almost head-on as it was flying at some 10,000m and detonated to the left and above the cockpit.

The forward section of the aircraft was penetrated by hundreds of high-energy objects. Three crew members in the cockpit were killed immediately and the airplane broke up in the air. Business class tore away from the fuselage almost instantly and crashed, while the rest of the plane flew another 8.5km before plunging to the ground.

A fierce fire broke out in the centre of the plane and engines when they hit the ground. Wreckage was distributed over various sites within an area of 50 sq km.

The investigators explicitly ruled out theories including metal fatigue, existing damage to the plane, exploding fuel tank and fire or explosives on board.

2. Buk missile system used

The warhead was carried on a class of missile installed on the Russian-made Buk surface-to-air missile system. The conclusion is based on the damage pattern found on the wreckage caused by the blast and the impact of fragments, analysis of the explosive residues and the distinctive "bow-tie" shape of some of the fragments.

The Buk missile is made by a state-controlled Russian company called Almaz-Antey. The company claimed its initial investigation found that the plane was downed by a model of Buk no longer used by Russian forces, but was still part of the Ukrainian military arsenal.

In its own report, Almaz-Antey said if the plane was hit by a Buk, it was fired from the village of Zaroshenske, which Russia claims was under Ukrainian government control at the time of the crash.

3. Passengers barely aware of attack

Investigators believed that many of the passengers likely died almost instantaneously. But they did not rule out that some "remained conscious for some time" during the minute to 90 seconds that it took for the plane to crash. However, since the missile strike was "entirely unexpected... there was hardly any time for a conscious response," said the report.

Some of the passengers and crew sustained "severe injuries" which likely killed them before the stricken plane crashed. And while the investigators could not say for sure "at which exact moment occupants died, it is certain that the impact on the ground was not survivable".

4. Ukraine should have closed air space; inadequate risk assessment

The inquiry found that the risks posed by the armed conflict in eastern Ukraine to overflying civilian aircraft were not adequately recognised. Ukraine should have closed its airspace to commercial traffic, while Malaysia Airlines and third party bodies such as the International Civil Aviation Organisation (ICAO) did not adequately consider the risks involved in flying over an area of conflict.

The report found that about 16 military planes and helicopters had been shot down in eastern Ukraine in the weeks before flight MH17 was downed. On the day of the crash, 160 flights flew over the area in question.

The report concluded that the current system for safeguarding civil aviation is insufficient to adequately assess the risks associated with flying over conflict areas.

5. Wide possible launch area

Calculations showed that the missile was launched somewhere in an area of 320 sq km in eastern Ukraine. All the territory within the area was in the hands of Russian-backed rebels at the time of the crash. But additional investigations, which fall outside the Dutch Safety Board's domain, are needed to confirm the launch location.

Key recommendations

- Nations in conflict should ensure they close their airspace in a timely manner.

- Airlines should carry out their own risk assessment and share information.

- ICAO should play a role in requiring airlines to account for the routes they select which pass over conflict zones.

- A person's nationality should be automatically added to passenger lists so that in the event of an incident, confirmation of identity can be done quickly.

SOURCES: AGENCE FRANCE-PRESSE, BBC