During those disasters unmanned aircraft surveyed wrecked roads, bridges and rail lines. They spotted oil and gas leaks. They inspected damaged cell towers that had left thousands unable to call for help. "Drones became a literal lifeline," former Federal Aviation Administration chief Michael Huerta told the agency's drone advisory committee in November. The drones used needed a special exemption from a set of FAA rules, known as Part 107, that normally require small drones to fly below 400 feet, stay within the operator's visual line of sight and avoid populated areas.