More info on AP [1]. Looks like a comms issue. The figures they quoted for the overhaul are absolutely insane - almost $45 billion (I used to work in telecom):

> "The government has been working to overhaul the outdated technology that air traffic controllers rely on since Congress approved $12.5 billion for the project last year."

> "Duffy has said that another $30 billion will be needed to complete the work, and the White House has begun lobbying Congress to approve it."

[1] https://apnews.com/article/flights-halted-airports-faa-f81b0...