So, we have:
- US military officials stating that they have satellite detection of the search radar turning on, followed by the IR blip of the missile being launched, followed by the IR blip of the plane being hit, followed by the plane crash.
- Video of what appears to be a missile being launched and hitting the plane.
- Video of the plane in flames in the air followed by the crash.
- Photos of the wreckage that appear to show penetration of the fuselage by external shrapnel of some sort.
- The PMs of both Canada and the UK saying they believe that the plane was shot down and have evidence to support it.
I mean, I get it, it's not official until the investigation is completed and the final report issued, but based on the above it seems pretty likely that the plane was shot down.