A US Defense Department representative said the Russian air force’s Tupolev Tu-154M plane’s flight over the White House, the Pentagon, the Capitol, and some other American facilities was conducted within the framework of the Treaty on Open Skies, according to Politico.

“The missions happen on a semi-routine basis,” said the Pentagon official, explaining that the Russians gave the required notice of at least 72 hours and that the mission has American personnel on board as observers.

“They usually come in and they list out what locations they want to fly over,” the official said. “We put together the flight plan and with a few exceptions—safety-wise or weather-wise—they are allowed to fly over pretty much the entire territory.”