WASHINGTON (Reuters) - Democratic U.S. presidential hopeful Dennis Kucinich may have been ridiculed for saying he had seen a UFO, but for some former military pilots and other observers, unidentified flying objects are no laughing matter.

An international panel of two dozen former pilots and government officials called on the U.S. government Monday to reopen its generation-old UFO investigation as a matter of safety and security given continuing reports about flying discs, glowing spheres and other strange sightings.

"Especially after the attacks of 9/11, it is no longer satisfactory to ignore radar returns ... which cannot be associated with performances of existing aircraft and helicopters," they said in a statement released at a news conference.

The panelists from seven countries, including former senior military officers, said they had each seen a UFO or conducted an official investigation into UFO phenomena.

The subject of UFOs grabbed the spotlight in the U.S. presidential race last month when Kucinich, a member of Congress from Ohio, said during a televised debate with other Democratic candidates that he had seen one.

Former presidents Ronald Reagan and Jimmy Carter are both reported to have claimed UFO sightings.

Most turn out to be misidentified aircraft, satellites or meteors. A panelist who once worked for Britain's Ministry of Defense said 5 percent of incidents cannot be explained.

But the sightings are often dismissed by authorities without proper investigations, UFO activists say.

"It's a question of who you going to believe: your lying eyes or the government?" remarked John Callahan, a former Federal Aviation Administration investigator, who said the CIA in 1987 tried to hush up the sighting of a huge lighted ball four times the size of a jumbo jet in Alaska.

The panel, organized by a group dedicated to winning credibility for the study of UFOs, urged Washington to resume UFO investigations through the U.S. Air Force or NASA.

"It would certainly, I think, take a lot of angst out of this issue," said former Arizona Gov. Fife Symington, who said he was among hundreds who saw a delta-shaped craft with enormous lights silently traverse the sky near Phoenix in 1997.

The Air Force investigated 12,618 UFO reports from 1947 to 1969 in what was known as Project Blue Book. Investigators concluded that the incidents posed no threat and there was no evidence of space aliens or a super technology in operation.

"Since the termination of Project Blue Book, nothing has occurred that would support a resumption of UFO investigations," the Air Force said on its Web site.

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