U.S. Government Web Portal Search:

USA.gov: UFO 

(USA.gov, Washington, D.C.)

A recommended Answers.USA.gov web page can be found among the search results: 

http://search.usa.gov/search?utf8=%E2%9C%93&affiliate=usagov&query=UFO

Wikipedia article: “USA.gov”:

http://en.wikipedia.org/wiki/USA.gov

(wikimedia.org image)