A Russian Air force spy jet has flown over a top secret missile base in Montana with the permission of the U.S government.

The position of the aircraft, which is allowed to fly anywhere it likes in the U.S under the Open Skies treaty, was posted on Twitter.

The jet was tracked near Malmstrom Air Force Base in Montana, where Intercontinental Ballistic Missile (ICBM) silos are based.

Part of its path was posted on the @CivMilAir account with the caption: 'Nothing to see here... Just a Russian Air Force Open Skies Treaty jet swoopin' down low & taking some high-res photos of US military installations.'

A satellite graphic of where the Russian Air-force jet was flying over Montana was posted on Twitter. It is permitted to fly in US airspace through the Treaty on Open Skies

The Russian jet was flying near or towards Malmstrom Air Force Base in Montana, where some of the intercontinental Ballistic Missile (ICBM) silos are based. The jet which is understood to be the one flying on the satellite graphic trajectory is pictured above

Russian military jets are permitted to travel in U.S. airspace through the Treaty on Open Skies, which has been signed by 34 nations in Europe and North America, along with Russia and Turkey.

The U.S. State Department claims that treaty allows unarmed aerial observation of military forces and activities over the territories of the nations who sign.

It is intended to improve mutual understanding and promote openness and transparency.

According to the Nuclear Threat Initiative, in March this year, Russia conducted routine surveillance flights over western US and similarly, the US conducted the first routine Open Skies surveillance in February, its first since 2017.

Monitors are on board the flight to ensure the surveillance missions are being conducted within the terms of the treaty, Defense News previously reported.

During the Cold War, a vast arsenal of nuclear missiles were placed in the Great Plains.

Hundreds of 'minuteman missiles', as they are known, remain active today and are an iconic weapon in the American nuclear arsenal.

Minuteman Missile Fields which were based in the United States during the Cold War and are still operational. The areas in black are missile fields that have been deactivated, the areas in red show missile fields that are still active

A deactivated Titan II nuclear Minuteman missile is seen in a silo at the Titan Missile Museum in Green Valley, Arizona

Minutemen missiles were first developed by America during the Cold War and formed an active part of the nuclear arsenal from 1962.

They were named for the Minutemen militias that fought in the Revolutionary War - small bands of self-taught fighters who were known for being ready to go 'at a minute's notice', like the missiles.

The military is thought to possess 450 missiles which cost $7,000,000 each and are fired from silos built into the ground and located across the country.

The first Intercontinental Ballistic Missile (ICBM) silos, where the missiles are located, arrived on the Great Plains in 1959 when Atlas sites were constructed in Wyoming.

Missile combat crew member 2nd Lt. Wesley Griffith prepares to close a three foot thick door inside a launch control center at Malmstrom Airforce Base. Malmstrom is home to hundreds of ICBM silos

It is understood that the jet was flying near or towards Malmstrom Air Force Base in Montana, where some of the intercontinental Ballistic Missile (ICBM) silos are based

Minuteman Missiles can be remotely controlled from Launch Control Centers miles away from the actual silos, allowing sites to be dispersed over a wide geographic area.

From the mid-1960s until the early 1990s there were 1,000 Minuteman Silos and 100 corresponding Launch Control Facilities for command and control, according to the National Park Service.

There are several reasons why Minuteman missiles were generally located in the Great Plains region as opposed to other parts of the US.

The Great Plains serves as the shortest distance to Russia, with one launch facility in South Dakota, being located approximately 5,100 miles from Moscow.

An artist illustration of a ballistic missile as it is fired into the sky

First Intercontinental Ballistic Missile (ICBM) silo locations are seen near Malmstrom Air Base

They were also located at sites far away from America's coastlines to offer additional warning time if submarines launched from off the coasts.

The first Minuteman came on-stream in Montana at the height of the Cuban Missile Crisis on October 26, 1962.

During the following year, 1,000 Minuteman's were placed across the central and northern Great Plains.

They were deployed in six wings out of Malmstrom Air Force Base in Montana, Ellsworth Air Force Base in South Dakota and Minot Air Force Base in North Dakota.

They were also deployed out of Whiteman Air Force Base in Missouri, F.E. Warren Air Force Base and Grand Forks Air Force Base in North Dakota.

Under the treaty, Russians are allowed to fly anywhere within 3,000 miles of the base.

However it was called into question after the US accused Russia of not allowing all members of the agreement to fly over its airspace.

Additionally, in September 2018, the US refused to certify equipment on board the Tu-214 aircraft for use in Open Skies missions before changing its mind after a week.