I will not deny the possibility, but there is no physical evidence that is available for public analysis. There are many unexplained circumstances, going as far back as cave drawings that showed man in the air. The massive drawings on the plains of Peru that are only recognizable by air. However there is nothing definitive, in centuries of mankind on this planet. And, the "spaceship" variety of UFO seems tied to the mid 20th century.
Just the Scriptures about the seed of Abraham outnumbering the stars, TO ME, implies at least man being on other planets.
Actually, I read that scripture in the exact opposite way. Perhaps we will definitively know in this lifetime. Very hopefully after.
I certainly think that our era is the era for all manner of things to change dramatically.
We shall see!