The world in general, and the US government in particular, seems to coalescing around the hypothesis that Malaysian Airlines flight MH17 was most likely shot down by separatist rebels in eastern Ukraine. There are several very good reasons to suspect this.
But there is also at least one pretty significant reason to doubt that eastern Ukraine's ragtag rebels really did this, or that if they did that they were operating entirely on their own. The military technology that shot down MH17 was, because of its high altitude, almost certainly a Russian- or Ukrainian-made Buk surface-to-air missile system. The Buk, sometimes called SA-11 by Americans, is no simple, shoulder-mounted missile: it is a complex system of one to three vehicles that requires extensive training to just turn on.
That's not something that a few rebels are going to randomly stumble onto, switch on, and start accurately firing at airliners 33,000 feet above the ground. Here's Moscow-based Alexander Bunin making the point eloquently, as translated by Russia analyst Kevin Rothrock:
Those are the controls of the Buk launcher system. To aim and fire a Buk missile, it typically requires three vehicles: the launcher, a commander vehicle, and a radar vehicles, all manned and operated in conjunction by people who know how to use them. (Some analysts say the launcher can sometimes be used on its own.)
This may help explain why, when a Ukrainian military cargo plane flying at high altitude was shot down earlier this week, the Ukrainian government suggested that the Russian military, not separatist rebels, was responsible. And why some analysts are still skeptical of the idea that this was purely rebels acting on their own. "Volunteer militia do not have the training to shoot sophisticated antiaircraft weapons," former US ambassador to Russia Michael McFaul tweeted.
It is possible, of course, that some of the rebels were former military and had thus received the training to operate a Buk system. Or that they mashed buttons at random and got very, very, very lucky. But Russia has been backing eastern Ukraine's separatist rebels very closely since the crisis broke out there a few months ago; it is hard to rule out the possibility that Russia may have trained the rebels in the use of the Buk system, hoping they would terrorize Ukrainian military planes (49 were killed in Monday's shoot-down) as they've been terrorizing ground forces.
Neither Russia nor the rebels has anything to gain by shooting down a civilian aircraft, so whoever fired at MH17 likely did so in a terrible error. But if Russia did train and encourage Ukrainian rebels to use the Buk system against aircraft then, error or not, this would raise serious questions about Moscow's complicity in the MH17 tragedy — and about how the world should respond.