Allegedly the rebels might have "Buk" missile systems that were taken in June from Ukrainian military base. However official Kiev claimed that those "Buk" systems were broken by Ukrainian military during their retreat from the base.
At the same time Ukrainian military has 27 "Buk" missile systems near Donetsk, they were set there on July 15th (according to Russian sources)
Apparently that is a common practice for high-flying aircraft to go through a zone of war conflict, it was done so before in Ukraine and other countries.
However the course of the plane has been altered(can be verified through historical information) by Ukrainian flight control (they were controlling the course of the aircraft and nobody denies it). Official version: "due to storms in the area of original flight course"
Note to the moderator: I know it's a veto on Ukrainian topic but could we at least talk about the plane crash?