For example one of the most extraordinary stories happened towards the end of World War II when German pilots claimed witnessing "fiery glowing object that followed their planes and then disappeared in wild maneuvers". These things, you could say were nicknamed "foo-fighters" and a conspiracy some thought to be secret military weapons.
The term "UFO" wasn't used until years later when the idea of "human space travel" sparked huge interests.
"...the number of fatalities in airline accidents caused by UFO's equals the number of motorists killed in vehicle collisions with unicorns."
Do you believe in UFO's?
http://news.discovery.com/space/fatal-distraction-can-ufos-cause-airline-accidents-121031.html