UFOs simply things at sky an observer cannot identify. May be airplanes, helicopters, planets, ball lightning, etc. Some scientists prove interstellar travel is fantasy, thus ETs can never come here. Fuel demands for interstellar travel can never be met. English Gaijin speak of aliens travelling at speed of light. That quite impossible. Matter can never travel even near speed of light. At speed of light, matter's mass become infinite, thus need infinite fuel supply, time intervals also become infinite. Time passage and length at direction of travel both become zero, thus other two dimensions become infinite. English Gaijin say travelers at speed of light age two weeks as we age twenty years at Earth. Actually someone age zero if could travel at speed of light. English Gaijin obviously not know Lorentz Equations. Time travel only fantasy. So are ET visitors. We Asians best at Science.