When Tokyo first learned of a U.S. "drone" downed by Iran while flying over the Strait of Hormuz last week, our initial reaction was rather obtuse. In Japan, drones are those available at shops in Akihabara. They usually have four small plastic rotor blades and can be remote-controlled from a long distance.

However, the drone shot down by Iran's Islamic Revolutionary Guard Corps (IRGC) on June 20 was by no means a miniature UAV. It was a U.S. Navy RQ-4A Global Hawk, a state-of-the-art surveillance aircraft as big as a jet fighter. In fact, RQ-4A is a 21st-century version of the U-2 spy plane.

On May 1, 1960, an American U-2 surveillance aircraft was shot down over Soviet territory by a Soviet Air Defense Forces SA-2 missile. The plane crashed but the pilot survived. He was quickly captured but returned to the United States two years later. The U-2 downing was so serious that a U.S.-Soviet summit meeting scheduled in Paris was canceled.