"It requires an extensive crew, a dozen men, and they all have to be highly trained," said Steve Zaloga, a senior analyst at Teal Group in Fairfax, Virginia, and an expert in Russian military technology. "Some of the tasks are less complicated, like more administrative tasks, but difficult training is required either way."

According to Zaloga, it's not as if the pro-separatists just found the launcher and pointed it at the aircraft. First of all, operating the launcher typically requires two or three other other radar vehicles and a supporting command system.

"All of the vehicles have to interact together at the same time, which is why the U.S. government is suspicious about who was helping them use the equipment," Zaloga said.

he powerful Cold War-era Buk missile system was built to protect Soviet army units from attacking aircraft during wartime. Unlike fixed-weapons used for national air defense, a Buk system in the field being used by separatist rebels likely wouldn't have information from air-traffic control centers, said Steve Zaloga, a senior analyst for the Teal Group Corp. in Virginia.

"The Buk system is not designed for peacetime use where it interacts with air traffic control," Zaloga said. "They would have seen a radar blip at 33,000 feet, but that's all they would have seen."