An anonymous air traffic controller has told Scripps News that the US ground stop began with a frequency issue at an East Coast airport on Friday afternoon. The controller says staff were not told what caused it or what repairs were under way.
According to the controller, the issue first prompted a ground stop at that airport, which Scripps does not name. Within minutes two more control towers reported similar problems, and the nationwide stop followed.
"Everyone knows frequencies went down somewhere but no one seems to have actually lost theirs"
The controller added: "Everyone texting their friends to figure out what's up and no one knows."
This account does not fit easily with the airline source who told CNN the fault involved network routers and started at Chicago Midway International Airport. None of these versions has been confirmed by the FAA, and none has been independently checked.
Scripps also reports, citing a congressional official, that neither the White House nor the Department of Defense knew the cause at the time. It says Duffy put the number of flights airborne when the stop was issued at more than 3,500, and said all landed safely.