According to physicist Seán Kirkpatrick, who heads the congressionally-mandated All-domain Anomaly Resolution Office, this alarming UFO activity can be attributed to one of two extraordinary sources: either a foreign power or "aliens." 

To be sure, the ramifications of either would be significant. But Kirkpatrick's comments, which come as he is about to retire after a 27-year defense and intelligence-focused career, are more intriguing because he also says that "none" of the hundreds of military UFO reports analyzed by his office recently "have been positively attributed to foreign activities."  

At the same time, Kirkpatrick and senior defense officials have ruled out the possibility that secret U.S. programs or experimental aircraft explain the phenomena.