Once upon a time, UFO conventions or seminars primarily attracted the lunatic fringe crowd -- those who arrived wearing alien costumes, tin foil hats and hoping to meet the alien man or woman of their dreams. Certainly, it was not the kind of event where serious scientists showed up.

That's all changing now, as evidenced by this week's 23rd annual 2014 International UFO Congress near Scottsdale, Ariz.

While there still exists a "purchase-an-ET-trinket" mentality fostered by an ever-present vendors room, the overall credibility climate has evolved where the topics presented during the week include government coverups, conspiracy theories, crop circles, alien abduction and former NASA scientists speaking out on how close we are to extraterrestrial contact.

Explore the out-of-this-world UFO-related items at the UFO Congress:

The IUFOC -- the biggest UFO conference in the world -- is presented each year by the Arizona-based Open Minds Productions, which offers the whole spectrum of UFOs and related unexplained phenomena through radio and television programs and their OpenMinds magazine.

"We have a lot more credible speakers than what the general public would expect for a UFO event," said Alejandro Rojas, one of the co-organizers and the master of ceremonies at this year's IUFOC.

The diverse speaker list for the UFO Congress includes:

Theologian Ted Peters, who has publicly stated that many religious leaders are ready to share a pew with aliens.

Former NASA scientist Richard Hoover, an astrobiologist engaged in research to find evidence of present-day water and fossilized and living organisms on Mars.

Astrophysicist Jeffrey Bennett, a former visiting senior scientist at NASA headquarters and one of the scientific leaders in the search for extraterrestrial life.

Former Army Col. John Alexander, a leading advocate for the development of non-lethal weapons, who has conducted non-lethal warfare briefings at the highest levels of government. He also organized an interagency UFO study and has taught psychokinesis in the military.

George Noory, host of "Coast to Coast AM," the biggest nightly syndicated radio program in North America, which features discussions of UFOs, paranormal phenomena, time travel, alien abductions and conspiracies.

One feature unique to this conference involves people who attend special experiencer sessions with therapists.

"We have therapists who put together [UFO] abduction experiencer groups. These are like group therapy where people can get together with others who have similar experiences. It is headed by therapists, and we have a lot of people who participate in those sessions, which are closed to the media because they’re just for therapy and for people sharing their stories," Rojas told The Huffington Post.

When it comes to claims of people who believe they've been abducted by aliens, society -- including skeptics and debunkers -- generally doesn't give any credence to such reports.

"I think it shows that people do believe passionately that they've had these experiences," said Rojas. "But it also shows a large number of people who feel they have these experiences. While the phenomenon is dismissed and whether or not these people are really speaking to extraterrestrials, because of the sheer number of people who believe this is happening to them, it's important for science and psychologists to pay attention to this and at least develop ways to cope with or deal with people who believe they're being abducted by extraterrestrials."

Rojas says he'd like the conference to help people learn and walk away with some knowledge and new ideas about interesting anomalous phenomena.

"I think there are a lot of people who are interested in subjects that are seen as taboo, and I don't think they should be. Hopefully, they'll feel more comfortable and notice there are a lot of very credible and grounded people who are interested in this topic."