news flash... FAA orders all flights grounded - no reason given, but the cause was inability of the air traffic control system at the FAA to keep up (and it's a funding issue that MIGHT coincide with hinting to a new democrat congress to approving funding). 7800 flights affected in 4 hours

The Federal Aviation Administration ordered a nationwide ground stop Friday afternoon, Nov. 13, halting departing flights at airports across the United States because of unspecified safety concerns. 

According to an advisory issued by the FAA’s Air Traffic Control System Command Center, the ground stop took effect at 2:54 p.m. Central time and will remain in place until further notice.

https://www.news9.com/oklahoma-city-news/faa-reportedly-issues-nationwide-ground-stop

https://www.yahoo.com/news/us/article/faa-says-nationwide-ground-stop-is-over-after-thousands-of-flights-canceled-021133009.html?.tsrc=1340&ncid=crm_-1285232-20261113-1074--A

follow up:

Transportation Secretary Sean Duffy blamed contractor L3Harris for the outage that halted departures nationwide Friday, saying a router involved in its work overwhelmed the air traffic communications network.