PARIS — A 15-month inquiry into the disintegration of Malaysia Airlines Flight 17 in the skies over eastern Ukraine has concluded that the aircraft was struck by a Russian-made missile, Dutch air accident investigators said Tuesday.

The findings — based in part on a distinctive shrapnel pattern that was found in the cockpit, near where the missile hit — come from a five-nation investigative team that retrieved and sifted through several tons of debris and human remains and even reconstructed the aircraft as part of its study.

“Flight MH17 crashed as a result of the detonation of a warhead outside the airplane above the left-hand side of the cockpit,” said Tjibbe Joustra, chairman of the Dutch Safety Board, using a common reference to the flight number. The explosion tore off the forward part of the plane, which broke up in the air. The crash killed all 298 people aboard; the investigation found that many died instantly, while others quickly lost consciousness. “It is likely that the occupants were barely able to comprehend their situation,” the board found.

While the findings stop short of assigning responsibility for the crash, a task that has been left to Dutch prosecutors, they appear consistent with a theory widely promoted by the authorities in the United States and Ukraine: that the plane, a Boeing 777, was shot down by Russian-backed separatists armed with an SA-11, or Buk, surface-to-air missile launcher.