In their book "Dark Mission, the Secret History of NASA," (Feral House, 2007), authors Richard C. Hoagland and Mike Bara present very persuasive information on NASA's alleged discoveries that indicate the strong possibility of extra-terrestrial life. They discuss purported findings on the moon by Apollo Astronauts, and on the surface of Mars captured in photographs taken during the Viking 1 mission, which, in their view, establish that extra-terrestrial life exists, or did at one time. The authors assert that NASA has withheld information on these findings, in part, due to a report by the Brookings Institution in the early sixties, which argued that affirmative findings of extra-terrestrial life is likely, and should not be disclosed. The authors go on to say, in substance, that NASA has been deliberately concealing information on their findings (of extra-terrestrial life) on "national security" rationales. I would highly recommend this book to anyone with an interest in the possibility of extra-terrestrial life, and the apparent findings of various NASA missions.
While I have never, to my knowledge, seen a UFO, I have always had a great interest in the subject. As such, I have read just about every prominent book on the topic of UFOs, alien abductions, crop circles, the Bermuda Triangle, and other mysteries. What never ceases to amaze me are the large number of credible sightings (those by military and commercial pilots, law enforcement, public officials, and the public in general) that are quickly refuted by the US Air Force or other government agencies, often providing the lamest of explanations. Moreover, many commercial pilots have gone on record claiming that reports of UFO sightings can be career ending. Why is this? Interestingly, the Belgian and French governments have released information on sightings made by their militaries, and a number of former Soviet scientists have also disclosed large numbers of UFO encounters.
Some of the major reasons given for non-disclosure, or outright cover-up, include concerns that knowledge that we are not alone, or that there are superior technologies and intellects, could result in the loss of national identity (i.e., people would begin to think of themselves as world versus US or other nation's citizens), the potential harmful impact it could have on organized religions, and the possibility of mass panic, similar to that which occurred after the War of the Worlds broadcast by Orson Wells in the 30s. Others argue that if the US or other governments have proof of extra-terrestrial life (and/or visitations), they would not want to disclose this information, especially if they are collaborating with any of these sources, which has also been alleged. For example, the late Colonel Philip Corso, in his book "The Day After Roswell," (Pocket Books, 2007), claimed that the Roswell crash not only occurred, but that technology obtained from the crashed craft(s) resulted in the development of many advances in our own technology, such as integrated circuitry, fiber optics, lasers, and Super-tenacity fibers. Corso, who was a member of President Eisenhower's National Security Council, was also the head of the Foreign Technology Desk, part of the Army's Research & Development Department. His position and credibility are unquestioned.
I would urge anyone with an interest in UFOs to research the JAL case, the Illinois UFO sightings, the RAF Bentwaters case, the Phoenix Lights sightings, and the 2010 O'Hare UFO sightings, for starters. Many excellent books and articles have been written on these and other cases by highly credible researchers, many of whom have, unfortunately, been ridiculed for their stances. MUFON is also an excellent resource, and a subscription to their Journal is both interesting and enlightening.
I, for one, believe the time has long passed for the public to be given accurate information on the existence of UFOS, as well as their origins and intents (if known). While I generally hate the term "It is what it is," it makes no sense to me for us to bury our heads in the sand or conclude that anyone who has claimed to have seen one of these things is hallucinating.