Under an international agreement, rival nations are allowed to spy on each other, which is exactly what happened Tuesday night when a Russian spy plane flew over Chicago.
The Russian plane, a Tupolev jet, departed Dayton, Ohio, and flew to Great Falls, Montana, likely collecting reconnaissance along the way, WGN reported Wednesday.
It is unclear exactly why the Russians decided to fly over Chicago, specifically, WGN reports.
An aviation expert told WGN that the flight path of the Tupolev suggests spying may not have been the primary motivator.
“It may have been avoiding storms,” said Ian Petchenik of FlightRadar24, an Internet-based service that shows real-time aircraft flight information.
“U.S. specialists on board will monitor the use of surveillance equipment and compliance with the provisions of the agreement,” A Russian military spokesperson said ahead of the flight, according to WGN.
Under the Treaty on Open Skies, member nations are allowed to conduct pre-arranged aerial surveillance over each other’s territories to give members the chance to confirm other members are abiding by military treaties.
The Treaty on Open Skies went into effect in 2002, allowing its 34 member nations to conduct the aerial surveillance missions with unarmed planes. Other member nations include Canada, Germany, Spain, Sweden, Turkey and the United Kingdom.
This isn’t the first Russian spy plane to fly over U.S. soil.
Russia’s first mission in 2019 came on March 28 and 29, when they flew a Tu-154M plane equipped with electro-optical imaging systems over Area 51 and other key sites in California and Nevada.
Between April 25 and 27, Russia conducted another round of missions over two of the United States’ top nuclear laboratories and other key sites.
The U.S. military has had its share of reconnaissance missions over Russia, too. In February, the United States conducted three missions over Russia, with Russian observers traveling with the U.S. crew, per treaty procedures.
“The United States has conducted three Treaty missions over Russia so far in 2019,” Pentagon spokesman Johnny Michael told Fox News in March before a flight over Russia. “Per Treaty procedures, the United States will inspect the aircraft and U.S. observers will be on board the Russian aircraft to monitor all phases of the observation flight over U.S. territory, to ensure Treaty compliance.”
Russia and the United States were unable to agree on letting either conduct a mission over their territories in 2018 due to raised tensions between the nations.
Russia’s Sergei Ryzhkov, the chief of Russia’s Nuclear Risk Reduction Center, accused the United States of violating treaty agreements with unauthorized imaging equipment.
“In breach of the Open Skies Treaty provisions, the head of the U.S. delegation refused to sign the final document, without giving any explanations or reasons, and citing direct instructions from Washington,” Ryzhkov said, according to the Tass news agency.