Project Blue Book Case #1556. On July 23, 1952, an unidentified object was observed along the Boston-to-Provincetown air corridor over Cape Cod Bay, Massachusetts. The hyphenated designation suggests the object was seen in transit between the two cities — possibly by an aircraft crew or ground observers tracking it along its path.
This corridor crossed Cape Cod Bay, one of the most monitored waterways on the East Coast. Naval facilities, Coast Guard stations, and Otis AFB's air defense radar all provided overlapping coverage of the area. The corridor was also a busy commercial air route connecting Boston's Logan Airport with Cape Cod destinations.
July 23, 1952, was during the peak week of the great wave — the same day as the South Bend, Indiana, sighting and just three days before the second Washington, D.C., radar event. Reports were pouring in from across the country at unprecedented rates.
The object traversed a well-monitored area without being identified by any of the military or civilian systems that covered the corridor. The case was classified "Unknown."