A notice given last week wrote off 750 miles squared of land that lies near a number of significant practice targets.
It includes a training post for Joint Terminal Attack Controllers and other integration exercises.
The restricted area also encompasses Desert Dry Lake, which sits just 30 miles away from Area 51.
The initial set of NOTAMs stretched from August 8 until August 12.
In addition to this, ‘Janet’ flights – a secret airline that only serves Area 51 – were spotted flying out to the area and surrounding installations.
This is thought to suggest that a major test event, or series of events, is taking place.
At the same time, it could simply be routine testing by the Trump administration.
Increased attention on Area 51 has fuelled a number of theories from various analysts and ordinary citizens alike.
Some feel that the US government is hiding aliens in the military base, away from public view.
They feel the remains from an alleged UFO crash near Roswell in 1947 are being concealed.
Ufologist James Abbott says that too many people have made allegations against Area 51 for the military site to be a routine one.
He added: “If – and it’s a very big if – the US government has come into possession of some incredible material or technology which could not have originated on this planet, Area 51 would be at the top of anyone’s list for researching it.”
Last month over a million people signed up to a Facebook event pledging to storm Area 51.
Lincoln County Sheriff Kerry Lee told CNN ahead of the event the town of Rachel is too small to handle two million people storming the US base.
He said: “I cannot believe it’s gotten this much attention. We deal with this on a weekly basis but nothing to this scale.”