happened before

https://www.nytimes.com/live/2026/11/13/us/ground-stop-natio...

That tool was first unveiled for the Washington, D.C., area airports two months ago, on a day when problems with air traffic communications failures also grounded hundreds of flights, after a circuit failed and it was discovered that contractors had accidentally ripped through a fiber line that was supposed to serve as its backup.

extraordinarily unlikely

Hm, only international ones though, and only at coastal airports. I guess oceanic airspace is less affected by whatever this is?