Tjibbe Joustra, chairman of the Dutch Safety Board, said in a telephone interview from The Hague that a final report would be issued sometime in the middle of next year and that investigators hoped to clarify “the type of object that penetrated the plane.”

The preliminary report’s most striking passages related to the moments just before the aircraft was hit, presenting a picture of a humdrum journey disturbed only by bad weather and clogged flight corridors.

The pilots’ last communication with air traffic controllers in the Ukrainian city of Dnepropetrovsk, according to the report, was a routine, three-second confirmation of the flight’s intended path through an aerial mile marker, or waypoint, known as an RND. “Romeo, November, Delta Malaysian, one seven,” a pilot reported. Less than a second later, the cockpit and the front fuselage of the eastbound plane were hit by a shower of “high-energy objects from outside the aircraft.” “Data from the flight data recorder and the digital cockpit voice recorder stopped at 13:20:03 hours,” the report said. “No distress messages were received from the aircraft.”

Nick de Larringa, the European editor of IHS Jane’s Defense Weekly, said that while not providing any definitive answers, evidence presented by the Dutch strengthened a view promoted by Washington and authorities in Kiev, the Ukrainian capital, that pro-Russian rebels shot down the aircraft using a Buk surface-to air-system. The Dutch report, he said, “does a lot to disprove the other theories but does nothing to disprove the Buk theory.”

Vladimir Chizov, Russia’s ambassador to the European Union in Brussels, said that the Dutch report shed no significant light on what had happened and said Russia, unlike the West, had stayed interested in the fate of Flight 17. “Until today, it seemed as if the whole crash was forgotten for several months by everybody except Russia — and perhaps Malaysia,” he said. “There was silence.”