To say access to the base is limited is an understatement. The base and its activities are highly classified. The remote location helps keep the activities figuratively under the radar, as does the proximity to the Nevada National Security Site, formerly the Nevada Test Site (NTS), where nuclear devices are tested. To gain access you need top security clearance as well as an invitation from the highest levels of the military or intelligence community.
The government has gone to a lot of trouble to make it difficult for anyone to see what’s going on inside Area 51. Even today, Area 51 is surrounded by thousands of acres of empty desert landscape, and the Air Force has withdrawn lands from public use to help keep the base hidden from snooping eyes.
Everyone who works at Area 51, whether military or civilian, must sign an oath agreeing to keep everything a secret. Buildings at the site lack windows, preventing people from seeing anything not related to their own duties at the base. By some reports, different teams would work on similar projects at the same time, but their supervisors would keep each team ignorant of the other team’s project. When testing a secret aircraft, officials ordered all uninvolved employees to stay inside until the test flight was over and the aircraft returned to its hangar.