There is another, more likely explanation, one that has repeated scientific documentation in many similar incidents: real but not physical. That is, they are probably fallen angels--demons--who are visiting our realm. For details, please see Lights In the Sky & Little Green Men: A Rational Christian Look at UFOs and Extraterrestrials, by astrophysicist and longtime UFO analyst Dr. Hugh Ross.
In Judaism there is no such thing as fallen angels or conflict in heaven.