A national radar outage would do it. This would be a bigger story. Everyone needs it to forecast. However it doesn't seem to actually be offline. So I don't think it was a very long outage if it did go down.
Can you fill in the blanks here? My attempt: "China would never spy on us, but because of the implication they would put 50k of our citizens currently in the air in mortal danger"?
"January 11, 2023. All U.S. departing flights were halted for several hours after a computer outage crashed the FAA's Notice to Air Missions (NOTAM) pilot notification system"
9/11 was different, that also required all planes to land, more or less, as quickly as possible and not continue to their destinations (unless that was timely, I suppose). This one is a departure ground stop, no more planes going up. Planes in the air haven't been ordered to land yet.
https://www.weather.gov/afc/radaroutage
"January 11, 2023. All U.S. departing flights were halted for several hours after a computer outage crashed the FAA's Notice to Air Missions (NOTAM) pilot notification system"
9/11, 2023 and today are the only three times.
https://news.ycombinator.com/item?id=50489641