The strange catlike voice that the air traffic controller heard could well be an encrypted communication from the unknown craft. But who were they talking to on an open frequency, and why was a secret aircraft in controlled airspace? It’s all very strange.
Story Source:
http://www.dailymail.co.uk/news/article-1361878/Russian-flight-controllers-UFO-aliens-speak-cat-like-language.html?ito=feeds-newsxml