Ukrainian president Petro Poroshenko called the crash “a terrorist act” and insisted that “the Ukraine armed forces did not fire at any targets in the sky.” Meanwhile, the official Russian news organization RIA Novosti quoted the head of Russia’s Federal Air Transport Agency as saying that “the responsibility [for flight safety] falls on the Ukrainian side.” (Bracketed insertion RIA Novosti’s.) Alexander Boordai, the leader of the Donetsk People’s Republic, the self-declared breakaway region in Eastern Ukraine, made a more explicit accusation: “It was either Ukrainian aviation or anti-missile defense” that downed the plane. Ukraine’s rebel militias, he said, simply didn’t have the capability to take down a civilian airliner flying at MH17’s altitude.

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.”