Shell R. Alpert, a United States Coast Guard photographer at the Salem, Mass., air station photographed what appear to be unidentified flying objects flying in a "V" formation at 9:35 A.M. on July 16, 1952, through a window screen. 

WASHINGTON - A Pentagon office studying unidentified aerial phenomena, better known as UFOs, has determined that nearly 200 recently reported sightings were "unremarkable" and possibly can be attributed to routine objects found in the air, including drones, balloons and clutter, such as plastic bags.

The All-domain Anomaly Resolution Office, established last summer, analyzed 366 reports gathered as part of a new push by the government to encourage reporting of unidentified flying objects, which have frequently occurred near military installations and naval vessels. The review left more than 170 reports uncharacterized, some of which "appear to have demonstrated unusual flight characteristics or performance capabilities, and require further analysis," according to a report submitted to Congress this week by the Office of the Director of National Intelligence, which has worked with the Pentagon to try to determine the nature of the objects.