"Instead our country needs to reopen its official investigation that it shut down in 1969," Symington said. "We believe that for reasons of both national security and flight safety, every country should make an effort to identify any object in its airspace," said a statement from the 19 former pilots and government officials from around the world.

The subject of UFOs came up in a recent debate among US presidential candidates, with Democrat Dennis Kucinich saying he once saw a UFO - making him the object of ridicule and jokes by late night television comedians. Sceptics say UFO sightings are merely aircraft, satellites or meteors re-entering the Earth's atmosphere. But the retired pilots spoke to a sympathetic audience of UFO "believers" who heard them recall their encounters with seemingly other-worldly objects appearing out of the sky.

"Nothing in my training prepared me for what we were witnessing," said James Penniston, a retired US Air Force pilot, as he described seeing and touching a UFO when he was stationed at a British air base in Woodbridge. He said he saw an inexplicable triangular craft in a clearing in the woods with "blue and yellow lights swirling around the exterior".

The UFO was "warm to the touch and felt like metal," Penniston said. One side of the craft had pictorial symbols and "the largest symbol was a triangle, which was centred in the middle of the others," he said. Then after 45 minutes the light from the object "began to intensify" and it then "shot off at an unbelievable speed" before 80 Air Force personnel, he said. "In my logbook, I wrote 'speed: impossible'." Rodrigo Bravo from Chile's air force said UFOs needed to be studied but lamented that the media often belittle the sightings.

"Sadly the UFO subject has been contaminated with false information, out of touch with reality, provided by unqualified people to the media," Bravo said. "One of our most important civil aviation cases occurred in 1988, showing that unidentified flying objects can be a danger for air operations," he said.

"A Boeing 737 pilot on a final approach to the runway at the Puerto Montt airport suddenly encountered a large white light surrounded by green and red." The pilot took a sharp turn to avoid a collision, according to Bravo. The panel included a former Iranian fighter pilot, Parviz Jafari, who said in 1976 he tried in vain to fire from his jet at an "object which was flashing with intense red, green, orange and blue light" over Tehran.

But when he approached, "my weapons jammed and my radio communications garbled". A former Air France captain, Jean-Charles Duboc, said in 1994 he and his crew saw "a huge flying disc" near Paris with a diameter of about 300 metres that left no sign on radar.

The disc "became transparent and disappeared in about 10 to 20 seconds," Duboc said. The former pilot said like other major airlines Air France was mindful of its image and it was difficult to raise the subject of UFOs. A former official with the Federal Aviation Administration, John Callahan, said government agencies discourage inquiries into UFOs.

"'Who believes in UFOs?' is the kind of attitude of the FAA all the time," he said. "However, when I asked the CIA person: 'What do you think it was,' he responded 'a UFO'."

When Callahan suggested the government tell Americans about a UFO, the CIA official allegedly told him: "'No way, if we were to tell the American public there are UFOs they would panic."' AFP