My best guess is that UFO's probably do exist, but they probably have little to do with aliens (not discounting aliens altogether though). I think most events UFO-related (outside of abductions) are military related. I think experiences involving contact and the perception of being inside an alien vessel is more likely hallucinatory (whether "real" or not).
"Science without religion is lame. Religion without science is blind" - Albert Einstein
"The Mighty One appears, the horizon shines. Atum appears on the smell of his censing, the Sunshine- god has risen in the sky, the Mansion of the pyramidion is in joy and all its inmates are assembled, a voice calls out within the shrine, shouting reverberates around the Netherworld." - Egyptian Book of the Dead
"Man fears time, but time fears the Pyramids" - 9th century Arab proverb