In a rare, public U.S. Congress hearing held for the first time in 50 years, a top defense official told lawmakers that an increasing number of unidentified flying objects have been reported in the sky over the past 20 years. "Since the early 2000s we have seen an increasing number of unauthorized and/or unidentified aircraft or objects in military controlled training areas and training ranges and other designated airspace," Scott Bray, deputy director of Naval intelligence, told a House security panel. However, he said the Pentagon had detected nothing that would suggest it's anything non-terrestrial in origin behind these phenomena. On the other hand, Brey also did not definitively rule out that possibility. Watch this video for more details.