It's likely that the missile that downed the Malaysia Airlines plane yesterday was a relic of the Cold War era known as a "Buk."
Here’s what we know about the Soviet-era missile system:
What is a Buk missile?
The Buk is a surface-to-air missile that can shoot down airplanes flying up to 13 miles off the ground.
It looks like the lower half of a tank or truck, with a few anti-aircraft missiles on the top and was developed by the Soviet Union in the early 1970s.
What does "Buk" mean, anyway?
Buk means “Beech Tree” in Russian. During the Cold War, NATO’s code name for the Buk was "the Grizzly.”
How many of them exist?
There are several hundred Buk missile systems out in the world today, in the hands of about a dozen countries, says arms control expert Igor Sutyagin with the Royal United Services Institute in London. Russia, Ukraine and other former Soviet republics are known to have them. Syria, which has bought weapons from Russia for years, has also been known to own the systems.
Who has them now?
There is no official registry of where each Buk system is, but the United Nations and the Stockholm International Peace Research Institute keep lists that attempt to keep track of these and other weapons. Individual countries also try to track the weapons through their own intelligence agencies.
How could one have ended up in Ukraine?
There are a few theories on the origins of the Buk missile system that allegedly shot down the Malaysian passenger jet. The Ukrainian military inherited some Buks after the Soviet Union collapsed. It's possible that pro-Russian rebels captured one from the Ukrainian army. Or, it could have come from a Russian military commander, either through official channels or on the black market.
Why do weapons from that era end up in different places?
It’s not uncommon for old weapons from Russia and the U.S. to have second and third lives beyond their original owners. Military officials sell old equipment to other countries, often at bargain prices.
“The United States is anxious in many cases to provide allies with military capabilities that don’t bust their budget,” says Bruce Bennett, Senior Defense Analyst with the Rand Corporation. The sales are legal, and governments aren’t required to report the movements of those weapons around the globe, though the UN and SIPRI both try to keep track.
It’s even more difficult to know how many smaller, less conspicuous Soviet-era weapons are circulating around the world's conflict zones illegally.