An internal Alaska Airlines message says the problems behind the nationwide US ground stop involve radar as well as communications, according to CNBC, which has seen the message. It is the first report that radar is affected, not only communications.
Separately, two law enforcement sources told CBS News that the TSA is still investigating the root cause. One of those sources said the issue concerns radio frequencies and how pilots communicate with one another.
That CBS account is the first sourced word that the TSA is looking into the cause. It also lines up with earlier reports from the Washington Examiner, The Air Current and airline crew messages pointing to radio frequency outages.
The FAA has not confirmed either the radar problems or the radio frequency explanation. Its spokesperson has so far said only that there is a communications problem affecting Air Route Traffic Control Centers, which matches Transportation Secretary Sean Duffy's statement on Friday.
The Alaska Airlines message and the CBS sources are unofficial and have not been independently checked. Neither Duffy nor the FAA has said whether a cyber attack is suspected.