Baz Ratner/REUTERS
The border is currently a war zone with sustained fighting between the Ukrainian government and pro-Russian separatist rebels. And within the past month, the separatists have brought down a number of Ukrainian military aircraft.
The cause of the crash isn't conclusively known at the moment. Pro-Russian separatists may have nothing to do with it. But they have been successful in destroying aircraft in recent months of the conflict.
Armed with Man-Portable Air
At least 10 other Ukrainian aircraft - all of them significantly lower-flying than a Boeing 777 - have been shot down since the rebels started using MANPADS according to a count kept by military aviation expert David Cenciotti, including five Mi-24 Hinds, two Mi-8 helicopters, one An-2, one An-30, and the Ukrainian transport plane.
According to an adviser to the Ukraine Interior Minister, the plane was shot down by a Buk ground-to-air missile system.
The pro-Moscow separatists have denied responsibility for shooting down the Malaysian flight, according to The Interpreter.