Russian and NATO spy planes regularly fly over each other’s territories, photographing military equipment and monitoring where forces are located. It’s all done with representatives from the observed country on board under the Treaty On Open Skies. Signed in 1992, the treaty has served as a confidence-building measure, allowing 34 countries to conduct observation flights and share the collected data with other members, if requested. But it may soon join the list of dead agreements born out of the end of the Cold War.