Airline operators cannot take it for granted that an open airspace above a conflict zone is safe, according to the findings of a probe into last year's downing of Malaysia Airlines Flight MH17 over eastern Ukraine.

In its final report on the tragedy, the Dutch Safety Board (DSB) said that in light of their responsibility for a safe flight operation, operators should carry out their own risk assessment for the countries of their destinations as well as those which they overfly.

The Dutch body said states were expected to contribute to this risk assessment by sharing relevant information about on-going conflicts.

"If states have relevant threat information regarding an airspace, it should be shared with operators and other interested parties through a timely and structured process.

"The safety of passengers, crew and aeroplane can be improved if states make this information available to all operators, not only to operators under their control," the report said.

The DSB has concluded that the Malaysian Boeing 777 plane was shot down by a surface-to-air BUK missile while cruising at 33,000 ft over rebel-held eastern Ukraine, killing all 298 people aboard.

Those killed on the Amsterdam to Kuala Lumpur flight included 43 Malaysians.

The report noted that on July 17, 2014, the day of the MH17 crash, the use of the airspace above eastern Ukraine was restricted below 32,000 ft, with the airspace above that altitude open to civil aviation.

The Dutch safety body said it was thinking of a stricter redefinition of the responsibility of states for their airspace as well as a more pro-active role for the International Civil Aviation Organisation (ICAO).

The report noted that between the end of April and July 17, 2014, the armed conflict in eastern Ukraine expanded into the airspace, with reports of at least 16 Ukrainian armed forces' helicopters and aeroplanes shot down.

"During this period, neither Ukraine nor other states or international organisations issued any specific security warnings to civil aviation about the airspace above eastern Ukraine," it said.