A small gyrocopter that flew through miles of the nation’s most restricted airspace before landing at the U.S. Capitol was “indistinguishable” on radar from non-aircraft such as a flock of birds, a kite or a balloon, the head of the Federal Aviation Administration said Wednesday. FAA Administrator Michael Huerta told a House committee that the slow-moving gyrocopter appeared as an “irregular symbol” on radar monitored by air traffic controllers. Huerta and other officials said the small, unidentified object did not pose an apparent threat before landing on the Capitol’s West Lawn April 15. Forensic analysis conducted later identified a slow-moving...