Four years ago this week, a plane full of innocent people just going about their lives - returning home, heading for vacation in Malaysia, flying to an international AIDS conference in Melbourne - unwillingly became a pawn in a war they played no part in before that day. On July 17, 2014, someone in an Ukrainian war zone looked up and thought they saw enemy military aircraft overhead. So they positioned their Russian-made missile and fired. What happened afterward would be a subject of debate - and a source of international tensions - to this day.