BelieveItOrLeaveIt

History Channel covered a show on UFOs and Vortex Phenomenon, where they mentioned that there are statistically significant more sightings of UFOs at sites where the ancients build some special monuments of spiritual significance, associated with some high energy centers caused by earth's geo-magnetic-electric fields.

These places are at Stonehenge, Sedona Arizona, and Hudson Valley (where there are some ancient man-made cave-like structures)>. There was a time-series picture shown of an UFO-craft making a vortex-like disappearance into unknown.

(Please note vortexes are associated with Black Holes, White Holes/Bing Bang, Bermuda Triangle, Yonaguni - Japan's Bermuda Triangle, Hurricanes, where funnel shape energy gradient - magnetic/electric/gravity/gravity/pressure)

Strangely, in the video series on Mexico UFOs sightings, there is mention by the native Americans, based on their ancestor's passed on stories, that these sites to draw energy from Earth's Electro-Magnetic Anomaly Centers, and perhaps use it to escape to another dimension.

There are petroglyphs with UFO Saucer like drawings in the paintings. There are a lot of unsolved mysteries about Americas - like the sophistication in their building technology which even today the modern technology can not replicate, Inca Lines with Air-Strip, Giant Figures Carvings on Desert Bed which only can be seen from the space, Crystal Skulls which even today's Laser can not craft so exquisitely with 3D Lathe/NC/Robotic Machines, Model of Fighter-like-Plane found in ancient sites, sophistication in their Astronomy and Math, Mechanical Calendering, submerged highways with massive stones overlaid, Machu Pichu, and so on.

Similar time travel-hypothesis is being put forward by Scientists on Time and Space Travel.

More on at these sites:
http://www.insight-books.com/SDNA
http://www.history.com/video.do?name=UFO_Hunters

Just ignore or give benefit of doubt to the natives nationalistic/religious based views. You can not blame them considering what happened to their civilization since the conquest of Americas by the Colonial Powers.

Ships of Light - The Carlos Diaz UFO Experience Part 1