Given that MH17 was reportedly flying at 33,000 feet when it was shot down, such an attack would indeed represent a major feat for a nonstate actor. There are historical precedents for civilian aircraft being shot down by missiles, but one reason it’s a relatively rare occurrence is that the necessary capabilities tend to be under the control of governments. “There aren’t that many insurgent groups that have that kind of a capability,” says Max Abrahms, a terrorism specialist and professor of political science at Northeastern University.

“But in this case, it actually makes sense” that an insurgent group shot down the plane, he says. States may as a general rule have better weapons than insurgent groups, but “really that power asymmetry goes out the window when the nonstate actor has strong backing from a government. Particularly from a government as weaponized as Russia.”

As my colleague Alexis Madrigal has pointed out, it’s at least possible that separatists in eastern Ukraine have the technical capability to down an aircraft flying at 33,000 feet. And the rebels have repeatedly demonstrated the capability to shoot down Ukrainian military aircraft.

But an international civilian target is, obviously, different—which is why all parties are scrambling to blame each other. Abrahms is inclined to attribute the attack to the separatists. However, he says, “this was almost certainly a mistake.”

Whether or not it was a mistake, the incident could set a new precedent on the world’s battlefields. As governments have acquired better and better weapons, and either lost control of them as in Libya or given them away as in Russia, Abrahms says, “the quality of weaponry falling into the hands of these militants has gone way up.”