Dutch experts are due to publish the first report into what caused the Malaysia Airlines flight MH17 to crash in eastern Ukraine in July.
The Dutch Safety Board is leading an international probe to try to piece together evidence on what happened.
All 298 people on board, most of them from the Netherlands, died when the plane came down, amid reports it was shot down by pro-Russian rebels.
But the search for evidence has been hampered by heavy fighting in the area.
The Malaysia Airlines Boeing 777 was flying from Amsterdam to Kuala Lumpur when it crashed between Krasni Luch in Luhansk region and Shakhtarsk in the region of Donetsk.
Dutch aviation investigators are relying on information from the black box flight data recorders, air traffic control, satellite images and photos from the scene to compile the preliminary report.
While it is not the final report into the crash, Tuesday’s findings are significant because they will be the first official account of what happened, says the BBC’s Anna Holligan in The Hague.
However, it will not attribute blame or liability for the crash, she adds.
Experts from the UK, Germany, Australia, Malaysia, the US, Ukraine and Russia are collaborating on the case.
The board says it expects the final report to be published within a year.
Ukraine’s government and several Western leaders say there is strong evidence that pro-Russian separatists shot down the plane with an anti-aircraft system known as Buk.
Russia has consistently denied allegations that it had supplied any missiles or weapons to the rebels.