 Project 119L was a follow up to Project Skyhook, Project Mogul and Project Grandson.The balloons were used to monitor the Soviet Union for such things as nuclear tests, and returned photography of more than 1.1 million square miles (more than 2.8 million square km) of the Sino-Soviet bloc.Top-secret high-altitude balloon programs such as Moby Dick, Moby Dick High and 119L may account for many of the UFO sightings starting around the mid-20th century.