What could this really be?

This is one of the most famous photos taken during the American flying saucer wave of 1952. It was taken by Shell Alpert, a U.S. Coast Guard (USCG) seaman stationed at the USCG weather office in Salem, Massachusetts, on July 16. The USCG briefly investigated the case and issued a press release. Afterwords, the original negative was sent to Project Blue Book for analysis. The official air force report stated,