According to CNN that’s because they weren’t noticed by anyone at the time. The US discovered them by examining retrospective satellite data for signals we foun

According to CNN that’s because they weren’t noticed by anyone at the time. The US discovered them by examining retrospective satellite data for signals we found emanating from a recent (2021) balloon. Presumably that one didn’t travel over populated areas or it would have been noticed by the public as well. https://www.cnn.com/2023/02/10/politics/us-balloon-tracking-method/index.html https://www.cnn.com/2023/02/10/politics/us-balloon-tracking-...