By Angela Greenwood

SACRAMENTO (CBS13) — It’s an unusual sight to see, a Russian surveillance jet on the tarmac of Travis Air Force Base near Fairfield. It was first spotted last week and spent several days in the area.

So why is a Russian spy plane flying over California?

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Officials say the jet was flying with permission from the white house. The plane has been flying over some of the nation’s most sensitive military sites, places where even U.S. commercial jets are banned. There is a peaceful purpose to these missions that began in Northern California.

The aircraft is flown as part of the Treaty on Open Skies between the U.S. and Russian Federation, which took effect in 1992. Under the agreement, unarmed military planes from both countries are allowed to fly over each other’s territory.

The Tupolev 154 is equipped with sensitive electro-optical cameras capable of taking high-resolution photos while airborne.

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Data from the plane’s transponder shows it flew over Downtown Sacramento on its way to Travis last week. It also flew over other strategic military sites on the west coast including Point Mugu, Coronado Island, Camp Pendleton, 29-Palms, Vandenberg and Edwards Air Force Bases. It even took a trip north of Las Vegas where the Nevada test site and Area 51 are located.

An Air Force spokesperson said the plane was inspected for compliance before it took off from Travis. U.S. observers were also onboard the aircraft to monitor all phases of the flights.

The Air Force has its own version of an open skies surveillance plane, and so far this year, it’s conducted three missions over Russian sites.

These flights were part of Russia’s first mission over the U.S. this year.

The agreement is an effort by both countries to keep an eye on each other’s military assets as new controversies revive some Cold War-era tensions.

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There are 32 other nations that are also members of the open skies treaty. The Russian plane took off from Travis AFB on Saturday, which was also the day of the base’s annual airshow.