the 1952 washington, d.c. ufo incident, also known as the washington flap, the washington national airport sightings, or the invasion of washington, was a series of unidentified flying object reports from july 12 to july 29, 1952, over washington, d.c. the most publicized sightings took place on consecutive weekends, july 19–20 and july 26–27. ufo historian curtis peebles called the incident "the climax of the 1952 (ufo) flap" - "never before or after did project blue book and the air force undergo such a tidal wave of (ufo) reports."