We have historical evidence of top secret vehicles being revealed long after they were put into use that could do things no one knew about, but we have no evidence of alien visitors at all. Given the choice, I think it's just more logical to go with the Occam's Razor approach.
Do you think a secret could be kept today, like the stealth fighter or Manhattan Project was?
Phil
“The biggest problem people have is they don’t think they’re supposed to have problems.” - Hayes Barnard
