Aviator sightings of unknown objects date from the 1930s up to the present. Trained pilots and crews have had close encounters with objects exhibiting extraordinary performance characteristics unmatched by even the most advanced military aircraft -- one near-collision reported here even encouraged the U.S. Air Force to seriously consider the possible involvement of extraterrestrial spacecraft.This close examination of the history of air-to-air UFO encounters scrutinizes each perplexing case in the light of new evidence from official documents, recent scientific findings, and firsthand eyewitness testimony. Sometimes terrifying, these never-before divulged secret episodes will thrill and inform readers, and may even leave them reconsidering air travel plans.