"Isn't it a leap to say, 'UFOs exist,' and then say it's E.T.?" asked Cook. "Is it the only explanation?"
Woolsey told ABC News she agreed to appear on the panel because she's interested in government transparency.
Gravel, the former Democratic Alaska senator who ran for president in 2008, told ABC News he doesn't believe UFO sightings necessarily mean extraterrestrial life exists.
"We don't know, but the reason we conclude it's extraterrestrial is because there's no explanation of the phenomenon of all these sightings," Gravel said. He bemoaned "the American government keeping this information from the American public and the people of the world. ... There's no question that there's something going on that's not explainable."
At one point during the "hearing," Kilpatrick appeared to buy into theories of extraterrestrial life.
"What you all have unveiled is there's something out there, we're not alone," Kilpatrick said.
The Wednesday morning session, attended by 55 or 60 in a dim auditorium at the Press Club in downtown Washington, D.C., will be featured in an upcoming documentary being produced by Paradigm, the same group that arranged the event.
According to organizer Stephen Bassett, who founded Paradigm in 1996 as a political-advocacy and lobbying group to pressure the government to release information on UFOs, the whole event will wind up costing $600,000. Funding was supplied by a wealthy Canadian donor named Thomas Clearwater, Bassett told ABC News.
"Congress is out of the game. Let me tell you, the president is out of the game," Bassett told ABC News. "It is run within the military-intelligence community."
An earlier version of this story referred to all the former members of Congress as Democrats. Former congressmen Bartlett and Cook are Republicans.