The Air Force spokeswoman said the military was aware of the Facebook activity and warned that "any attempt to illegally access military installations or military training areas is dangerous."
The existence of Area 51 was formally acknowledged by the federal government in 2013, when the CIA released a classified report on spy planes that were tested there beginning in the 1950s.
But UFO enthusiasts and conspiracy theorists have long suspected that the base was devoted to the study — or even the captivity — of extraterrestrial life forms.
"We will all meet up at the Area 51 Alien Center tourist attraction and coordinate our entry," the Facebook event page said. "If we naruto run, we can move faster than their bullets. Let's see them aliens."
The "Naruto run" is a style of running associated with Naruto Uzumaki, the main character in the Japanese anime series "Naruto." It's a meme. To do the run, you tilt your torso forward, extend your arms out behind you, and sprint goofily.
As of Monday, more than 1 million people had responded to the post to say they were going to the September event. More than 900,000 others said they were interested.
Most seemed well aware that the post was made in jest. One Facebook user shared a detailed battle plan, involving two Naruto runner battalions running "full speed around the north and south flank" of the base. And a few commenters shared a meme that said, "If we all hit our vapes at the same time, we can use it as cloud cover so they won't see us coming."
Like other fake Facebook events, this one was mostly an invitation for people to create joke memes on Reddit, Twitter, YouTube and elsewhere. In addition to sharing implausible invasion tactics, internet users mused about how the aliens would fare in the real world after being freed from captivity by a horde of vaping heroes.
But as it turns out, some people may be taking the event seriously. The Little A'Le'Inn in Rachel, Nevada, which is close to Area 51, has gotten an unusually high number of reservations for a certain date.
"Oh, it's insane," Connie West, a co-owner of the inn, said in an interview on Sunday. "My poor bartender today walked past me and said, 'I hate to tell you, but every phone call I've had is about Sept. 20.'"
She added that many people had mentioned the Facebook post when they called to reserve the inn's rooms and recreational vehicles, all of which are now booked for that date — even though the Facebook post invited people to Amargosa Valley, which is hours away from the Little A'Le'Inn by car, and on the opposite side of Area 51.
"They're pretty serious," West said. "They're coming. People are coming."
In response to questions about the Facebook post, Laura McAndrews, an Air Force spokeswoman, said the Air Force does not discuss specific security measures. She noted that "the Nellis Test and Training Range is an area where the Air Force tests and trains combat aircraft."
This is not the first time military officials have had to respond to concerns about the possibly paranormal.
Earlier this year, the Navy seemed to officially acknowledge reported sightings of strange objects in the sky when it sent out new classified guidance on how service members should report what the military calls unexplained aerial phenomena, or unidentified flying objects.
And in 2017, The New York Times reported on a shadowy program at the Pentagon that has been investigating reports of unidentified flying objects for years.
But rather than infiltrate secret military sites, earthlings in search of evidence of extraterrestrial life may want to keep an eye on scientific explorations like the one taking place on Mars, or planned efforts to explore a moon of Saturn.
West said Area 51 is well guarded, with signs warning trespassers that they could face consequences, including prison time or deadly force, if they get too close. She said she expected people to try to breach the boundaries of Area 51 in September, though she wished they would not.
"There's going to be a force to reckon with," she said of the authorities guarding the base. "They have enough helicopters and military aircraft at Nellis Air Force Base."
Written by: Jaycey Fortin
© 2019 THE NEW YORK TIMES