The New York Times has reported on a US Government program to investigate sightings of UFOs (unidentified flying objects) - including revealing new footage taken from a fighter jet of an unknown craft.
The Advanced Aviation Threat Identification Program, which investigated a number of reports from military pilots who had seen aircraft they could not identify, was pushed forward by former Nevada Senator Harry Reid in 2007.
The Pentagon acknowledged the existence of the program this month, and officially the program lost its funding in 2012, but the Times reports that officials within the Department of Defence working at the Pentagon continue to investigate reports while also carrying out other duties.
In some cases, the craft were reported to have manoeuvred so quickly and unusually that they would defy the laws of physics.
In one video, released by the US Department of Defence in August, an unidentified object can be seen tracked by an F/A-18F's gun camera off the coast of San Diego in 2004.
The pilot of one fighter jet can be heard talking over the radio to another during the encounter.
"There's a whole fleet of them," one says.
"They are all going against the wind ... the wind is 120 knots ot the west.
"Look at that thing ... it's rotating."
Luis Elizondo - the intelligence officer who ran the initiative - resigned in October, and in his resignation letter called on Secretary of Defence James Mattis to take the efforts of the program more seriously.
Mr Elizondo recently told Politico that Navy pilots and other observers had seen aircraft with capabilities far beyond what we currently consider to be possible in the field of aerodynamics.
He also decried the lack of alarm expressed by the government, saying "If a Russian 'Bear' bomber comes in near California, it is all over the news ... these are coming in the skies over our facilities - nothing but crickets."
"Why aren’t we spending more time and effort on this issue?"
Mr Elizondo said the effort was continuing, and that he had a successor.