SAM Missiles
Can't imagine how anyone thinks Ukraine are responsible for this. They closed their airspace at altitudes threatened by MANPADS weapons which was how previous aircraft were downed in E. Ukraine. They had ATC control of the airspace over East Ukraine (they didn't over Crimea which was closed). They are not privvy to movements of Russian military equipment inside the rebel controlled area.
Blaming Ukraine for the shoot down of MH 17 is like blaming the police for a murder by not arresting the perpetrator prior to it happening. Absurd.