The U.S. military has issued a warning to a million people who have pledged to 'storm Area 51' - the secretive military base in Nevada.
The plan - titled 'Storm Area 51, They Can't Stop All Of Us' - was hatched on a Facebook group and is set for September 20 this year, at 3am, with attendees pledging to 'see them aliens'.
Air Force spokesperson Laura McAndrews said that the base 'is an open training range for the US Air Force, and we would discourage anyone from trying to come into the area where we train American armed forces.'
The US Air Force always stands ready to protect America and its assets.'
The plan has attracted thousands of people claiming they will attend.
It is widely believed to be a joke, with organisers saying, 'We can move faster than their bullets. Let's see them aliens.'
At the Area 51 base in Nevada, there is a 25-mile no-fly zone for civilian aircraft - so aerial views of the base are rarely seen.
But have they, as UFO fans believe, been working on secret technologies stolen from aliens? Or is the base simply a test-bed for hi-tech fighter aircraft?
Nigel Watson author of the UFO Investigations Manual, says, 'Area 51 has always been a magnet for those who believe the US Government knows a lot more about UFOs than they are prepared to reveal to the public.
'People like the late Boyd Bushman, a senior scientist who worked for Lockheed Martin, have declared that Area 51 is a base where extraterrestrial spacecraft and technology is stored and examined.
'Bushman believed in what he was saying. As long ago as 2008 he passed a polygraph test, during which he claimed he had worked on antigravity projects, alien technologies and had even met and photographed an alien, and examined at least 8 different types of alien spacecraft. Bushman also revealed that he had received death threats and that security personnel had attempted to discredit him and tried to keep him from talking to the public.
'They Can't Stop All of Us.' Thousands Sign Petition to Invade Area 51 to Find Those Aliens
'He said the aliens fly their spacecraft on a special flightpath that takes them through a shaft drilled on the side of a mountain near Area 51. He went on to say 230-year-old humanoid aliens from the planet Quintumnia lived at Area 51.
'This backs-up other claims of people who say they have worked on ET spacecraft at the base, but there is no solid evidence for their stories. Indeed, the extreme nature of these claims makes serious investigators shy away from this subject, and talk of UFOs and aliens is an effective way of hiding the real human technological activities at the site.
This article originally appeared on Yahoo UK