If Malaysia Airlines Flight 17 was shot down by Ukrainian separatists, those responsible likely didn’t know what they were shooting at and were probably operating outside what limited control the Donetsk People’s Republic has over its air defense system, experts in Soviet and Russian weapons system told The Daily Beast.

Ukraine’s government said the rebels used the Russian-made Buk surface-to-air missile system. Descended from the 1970s-era SA-6 Gainful, the Buk is in use throughout the militaries that make up the countries of the former Soviet Union, including Russia and Ukraine.

Known in Western parlance as the SA-11 Gadfly or SA-17 Grizzly, they were designed to defend the mighty Red Army from NATO planes as it would advance across battlefields in a Third World War. They are some of the most potent tactical surface-to-air missiles (SAM) in Russia’s arsenal, said the Teal Group’s Steve Zaloga, an expert on missiles.

It’s a sophisticated surface-to-air anti-aircraft system with a range of up to 25 kilometers high, putting Flight MH17 easily within range. Unlike the powerful, extremely long-range and much-feared Russian S-300 (also know as the SA-10 or SA-20) surface-to-air missile, the Buk is not tied into a national air defense system. The system’s operators have to rely on their own radar, which has limited capability. “Normally it is not netted into the national air defense system,” Zaloga said. “It would be netted into the army’s air defense network.”

“It’s not super high-tech, but it can do the job,” added retired Maj Raymond Finch, an expert in Soviet and Russian weapons systems at the Foreign Military Studies Office at Fort Leavenworth, Kansas. “It can go way high. It’s a deep strike.”

It takes a certain amount of training to set up and use, Finch said. And while he declined to specify who might have been operating any Buk system, he added that, “My guess is that some of the guys on the ground, in the region … are various grades of Russian military specialists.” He added that Ukraine has a number of former and retired Soviet Army officers who could have the expertise to operate a Buk system.

“The average guy off the sofa is not going to be able to operate this system.”

Still, distinguishing between civilian and military aircraft would be difficult if the system used was lacking the newer tracking systems that use radar signatures and national systems to tell which was which. “The more sophisticated models can,” Finch said. “I know that was the case in Iraq.”

Zaloga agrees. The Buk was likely relying on its own radars, he said. “They don’t have that type of information, they don’t know anything about the larger picture,” he said. “They only know what they see on their radar, and with that radar they have very limited data.”

The missile operators—relying on their limited information—may have mistakenly presumed that the Boeing 777 airliner was a military transport, like the Ukrainian An-26 shot down by rebels on Monday. “It definitely could have been an error,” Zaloga said. “I can’t imagine that anybody would take a deliberate shot at an airliner. I don’t think the Russian separatists are going to take a pot shot at a Malaysian airliner, and I don’t think the Russians are going to do that.”

Finch was more succinct in his initial opinion. “They got something on their radar screen, and they engaged it and now they’re like, ‘Oh shit, what have we done?’”

This is borne out by separatist leader and Russian intelligence official Igor Strelkov, who earlier today posted online “do not fly in our skies,” adding that his forces had shot down a plane. After the identity of the crashed airplane became known, Strelkov’s comments were scrubbed from the website. Separatists now deny having shot down the airliner or even possessing Buk systems, despite publicly capturing some in June from Ukrainian forces.