Evidently the U.S. NOTAM system failed at around 7am this morning. Subsequently all commercial airline flights were grounded till it could be restored. Why? You can't dispatch an airplane if you don't know if the airport you are flying too is open, whether airspace is open or closed, or a number of other equipment or systems are operating.
One example, If the firefighting capabilities of an airport are degraded because of equipment failure, you might not be able to land at that airport since it no longer satisfies the AARF requirements for the size of your airplane.
Another example would be the failure of a single ILS airport if the weather made it necessary or it was being used as a destination alternate.
The bold is mine.
Biden addressed the FAA issue Wednesday before leaving the White House. He said he had just been briefed by Transportation Secretary Pete Buttigieg, who told him they still had not identified what went wrong.
"I just spoke to Buttigieg. They don’t know what the cause is. But I was on the phone with him about 10 minutes," Biden said. "I told him to report directly to me when they find out. Air traffic can still land safely, just not take off right now. We don’t know what the cause of it is."
https://www.foxnews.com/politics/faa-outage-white-house-says-no-evidence-cyber-attack-biden-briefed-grounded-flights

Well that gives me the warm and fuzzies!! Super Butt is on the case!!! How about tossing the FAA some of that infrastructure money you're sitting on Pete? Replace the Commodore 64 computers they are using.
Also, with power grids, hospitals, and numerous businesses being cyber attacked, how are they so sure so quickly it wasn't a cyber attack?
What's the point of an open door policy if inside the open door sits a closed mind?