The Bush administration has been flying surveillance drones over Iran for nearly a year to seek evidence of nuclear weapons programs and detect weaknesses in air defenses, according to three U.S. officials with detailed knowledge of the secret effort. The small, pilotless planes, penetrating Iranian airspace from U.S. military facilities in Iraq, use radar, video, still photography and air filters designed to pick up traces of nuclear activity to gather information that is not accessible by satellites, the officials said. The aerial espionage is standard in military preparations for an eventual air attack and is also employed as a tool...