Another high-altitude balloon has been tracked flying over U.S. territory, reviving concerns about surveillance and national security. We’re revisiting what’s known so far.

Biden officials held discussions with Beijing on Feb. 1 about the balloon, and discussed the impact disclosing the balloon to the public could have on the relationship with China.

Meteorologists Jeff Masters and Tomer Burg calculate that 14 of 83 U.S. balloon sites, or 17%, are doing partial or no launches. That includes two stations that aren’t launching because of a ...