The large mysterious drones reported flying over parts of New Jersey in recent weeks appear to avoid detection by traditional methods such as helicopter and radio. The devices do not appear to be being flown by hobbyists. Dozens of mysterious nighttime flights started last month and have raised growing concern among residents and officials. Drones are legal in New Jersey for recreational and commercial use, but they are subject to local and Federal Aviation Administration regulations and flight restrictions. Operators must be FAA certified.