A U.S. government report on UFOs said Friday it found no evidence of aliens, but acknowledged 143 reports of "unidentified aerial phenomena" since 2004 that could not be explained. Some of the most intriguing cases come from Navy pilots who reported seeing UFOs — and filming some of them — off the East Coast of the U.S. over a period of months in 2014 and 2015. The pilots, including some who have spoken publicly, say the mystery objects moved with exceptional speed, agility and acceleration that they had never seen before.