A preliminary report from US Intelligence claims that pro-Russian Ukrainian separatists shot down MH17 with a surface-to-air missile, according to the Washington Post, which is citing an unnamed US official. The separatists probably used an early version of the Buk anti-aircraft system, a sophisticated surface-to-air missile system:
"Our assessment is that Malaysian Airlines Flight 17 . . . was likely downed by an SA-11 missile, operated from a separatist-held location in eastern Ukraine," U.S. Ambassador to the United Nations Samantha Power told the U.N. Security Council on Friday.
She added that "because of the technical complexity of the SA-11," it was unlikely that the separatists could have effectively operated it on their own. "We cannot rule out Russian technical assistance," Power said.