Could So Many UFO Witnesses Be Right? Could all those UFO sightings be real?

Sept. 12, 2008 -- For decades, millions of people around the world have reported seeing UFOs hovering in their skies. It is a mystery that science has been unable to solve, and the phenomenon remains largely unexamined. Much of the reporting on this subject holds those who claim to have seen UFOs up to ridicule.

"UFOs: Seeing is Believing" takes a serious look at the phenomenon in today's world. The 90-minute special includes interviews with scientists searching for proof of life beyond earth and UFO witnesses who claim aliens are already here. Building on the original Peter Jennings report in 2005, David Muir reports on new sightings, as well as NASA's current search for life on Mars.

The program follows the entire scope of the UFO experience, from the first famous sighting by Kenneth Arnold in 1947 to the present day. Muir reports on a recent UFO sighting in Stephenville, Texas, where multiple witnesses reported seeing enormous lights moving in strange configurations on the evening of January 8, 2008. He interviews some of the most credible witnesses of the sighting and a radar expert who evaluated their claims and found something surprising in the data. Sophisticated animations approved by the eyewitnesses allow viewers to get a feel for the experience first hand.

The special draws on interviews with police officers, pilots, military personnel, scientists and ordinary citizens who give extraordinary accounts of encounters with the unexplained. While professional skeptics about UFOs speak out, including scientists who are leading the search for life forms elsewhere in the universe.

The special also examines the most recent advances in the search for life on other planets. This past summer, NASA's Phoenix Mars Lander, a robot that tests and analyzes soil on the planet, found conclusive evidence of water ice on Mars. You'll hear from scientists on the project about the real possibility of finding life on Earth's next-door neighbor.

ABC News explores the facts behind the mystery of the incident at Roswell, New Mexico, where, in 1947, the story goes, the U.S. Government collected the wreckage from a crashed flying saucer. And you'll hear from the people who claim they've been abducted by aliens.

Among the UFO cases presented:

Phoenix, Ariz., March 1997 -- Thousands witness what many believe was a huge triangular craft moving slowly over the city.

St. Clair County, Ill., January 2000 -- Police officers in five adjoining towns all independently report witnessing a giant craft with multiple bright lights moving silently across the sky at a very low altitude.

Today, if you report a UFO to the U.S. government, you will be informed that the Air Force conducted a 22-year investigation which ended in 1969 and concluded that UFOs are not a threat to national security and are of no scientific interest.

But leading theoretical physicist Michio Kaku told ABC, "You simply cannot dismiss the possibility that some of these UFO sightings are actually sightings from some object created by an advanced civilization because … on the off chance that there is something there, that could literally change the course of human history."