FAA abruptly issues national ground stop for all US airports

The Federal Aviation Administration issued a national ground stop for all US airports just short of 4pm ET on Friday due to what the agency described as "extraordinary circumstances and for reasons of safety."

The FAA ordered all departing traffic to remain grounded until further notice. The agency said inbound international flights will be managed on a case-by-case basis.

The ground stop came after the FAA reported air traffic control communications issues earlier on Friday. The agency initially halted traffic in Chicago due to these communications problems before expanding the order nationwide.

According to a report by the Air Current, the groud stop was caused by ATC frequency issues. 

The agency did not disclose a formal reason for the grounding.