What started as a tongue-in-cheek plan by UFO enthusiasts to storm a notoriously secretive U.S. Air Force base to “see them aliens” has turned into a national security issue. The U.S. Air Force has now offered a word of caution to the more than half a million people who said they would be attending the Facebook event “Storm Area 51, They Can’t Stop All of Us” in September: “[Area 51] is an open training range for the U.S. Air Force, and we would discourage anyone from trying to come into the area where we train American armed forces,”spokeswoman Laura McAndrews told The Washington Post. “The U.S. Air Force always stands ready to protect America and its assets.” Despite the warning, users are still posting memes theorizing the best way to break into the top-secret facility on the event page, where organizers said, “If we Naruto run, we can move faster than their bullets.”