UFO Flap
The word "flap" is ufology jargon for a period of dramatically increased UFO sightings and is sometimes referred to as a "wave". However UFO flaps are different from UFO waves in that UFO flaps are usually considered to be more localized and of a shorter duration ( less than a few weeks ). However both terms are often used synonymously and there are no definitive rules as to usage. One of the first widely recognized references to a UFO flap is in The Report On Unidentified Flying Objects, by Edward J. Ruppelt. Chapter 11 is titled "The Big Flap" and it describes a UFO flap which occurred during the summer of 1952.

The origin of the term is from the USAF. Ruppelt explains that it was used informally to describe a condition, or situation, or state of being of a group of people characterized by an advanced degree of confusion that has not quite yet reached panic proportions. HE goes on to add somewhat colorfully that it can be brought on by any number of things, including the unexpected visit of an inspecting general, a major administrative reorganization, the arrival of a hot piece of intelligence information, or the dramatic entrance of a well-stacked female into an officer's club bar.