By Will Grant, BBC News
A group of former pilots and government officials has called on the US government to re-open an investigation into claims of UFO sightings.
The group, which includes former military officers from seven countries, all say they have seen a UFO or have conducted research into the phenomenon.
However, the Air Force says nothing has happened in the past four decades to justify resuming investigations.
Every year thousands of people say they have seen UFOs in the United States and their claims are usually met with scepticism.
We want the US government to stop perpetuating the myth that all UFOs can be explained away in down-to-earth, conventional terms
Ex-Governor of Arizona
But this panel of former military, government and aviation personnel from countries around the world has urged the US government to take such claims seriously.
The group say the apparent sightings of hovering orbs, glowing lights and high-speed spacecraft are a national security concern and should no longer be dismissed.
After the attacks of 11 September, the group said in a statement, it was no longer satisfactory to ignore radar returns that could not be associated with existing helicopters and other aircraft.
The panel has called on the US military to re-open an investigation dormant since 1969, called Project Blue Book, in which more than 12,500 UFO claims were investigated by the Air Force.
For now, it seems their pleas have fallen on deaf ears - the US Air Force says nothing has changed that would support a resumption of the investigation.
But those who believe they have seen UFOs, know they have influential supporters.
Among those on the panel is the former governor of Arizona, Fife Symington, and last month, the Democrat presidential candidate, Dennis Kucinich, said during a televised debate that he'd seen a UFO.
UFOs are no joke, group says