As I understand it, there have been times when overflight of Afghanistan has been banned by some regulators because of this risk (amongst other reasons). The way that the CX captain told it to me, there are some bits of high ground in Afghanistan that are close to 20,000 feet above sea level. If, at that point, you're restricted in the cruise to something in the FL300-350 range ... well, he said that there were other airlines that had not been banned, and still planned overflights, so the crews simply turned off all their lights and watched the fireworks around them as they cruised overhead.