A low-flying Russian airplane created a buzz in the nation’s capital on Wednesday, but it turns out the surveillance flight over the Capitol, Pentagon and other sites was cleared by the U.S. government under a long-standing global treaty. The flight was permitted under the Open Skies Treaty.

Russia and the U.S. are signatories to the treaty, which allows unarmed observation flights over the territory of all 34 member nations. The flights are intended to foster transparency about military activity, reduce mistrust or misunderstandings and help monitor arms control and other agreements.

Dan Gaffney, a spokesman for the Pentagon, said he could not confirm the plane’s path until its mission was over. “A typical mission has several segments [flights] taking place over a few days,” Gaffney said. But the U.S. Capitol police issued a heads-up, saying an “authorised low-altitude aircraft” would enter restricted airspace over the Capitol between 11 a.m. and 3 p.m.