Pilot forum discussion - https://www.pprune.org/rumours-news/674910-us-wide-ground-st...

"Frequency outage", I think that translates to radio communications not working, until "22 Zulu" aka 22:00 UTC, 5 PM ET.

Microsoft outage related??

What are all the possible reasons to do this?

Has this ever happened?

Some more discussion: https://news.ycombinator.com/item?id=50489641

I guess some of their floppy drives must have given out.