Via AlMasdarNews.com,

A Russian Tu-154M-ON (NATO reporting name: “Careless”) reconnaissance plane has conducted a surveillance flight over US military facilities located on the west coast of the country, The Drive online magazine reported.

Russia TU-154M planes are certified to conduct "Open Skies" flights, via Flickr

The plane reportedly took off from Great Falls and flew over the Edwards Air Force Base, United States Air Force Plant 42, which is used to modernize and assemble various military aircraft, including strategic bombers, Vandenberg Air Force Base, as well as the Nellis Test and Training Range — also known as Area 51.

The reconnaissance flight was carried out according to Treaty on Open Skies provisions that allow for mutual aerial inspections of the signatories for the sake of verifying the fulfillment of disarmament treaties.

The mid-day flight on March 28th, 2019 appears to have originated out of Travis AFB, located near San Francisco, and continued on something of a highlights tour of American military installations in California and Nevada. It flew south over central California, passing near bases like Naval Air Station Lemoore and headed out over the Channel Islands. It then headed directly over Edwards AFB before meandering around Fort Irwin and on to Naval Air Weapons Station China Lake before hooking a right and heading toward Creech AFB in Nevada. It then headed north, directly into the NTTR — the most secure airspace in the United States along with Washington, D.C. — The Drive

The US threatened to suspend its participation in the treaty in 2018, claiming that Russia was not adhering to it, but the State Department later stated that Washington would not follow through on the threats.

Via The Drive/FlightRadar24: This is the medium alitidue imaging portion of the flight by the Tu-154M.

The Tu-154M-ON is a modification of the Russian Tu-154M LK-1, which is used in cosmonaut training programs, is specifically fitted for conducting aerial inspections.