A "flap" is defined as a series of sightings by multiple witnesses over numerous days. And they're rare. That's why the MUFON team is rushing to investigate this July, 2008 flap. Most witnesses in Bucks County, Pennsylvania, have little to offer but anecdotal testimony. However, the team discovers two witnesses who had multiple sightings and appear to have scientific corroboration for their claims. But scientific disagreements and government stonewalling, obscure what was thought to be an unambiguous investigation.