The Federal Aviation Administration issued a nationwide ground stop on Friday afternoon, disrupting hundreds of flights, after reporting communication problems affecting "multiple" air traffic control centers.
The issues were related to communications and radar issues, according to an internal message from Alaska Airlines, which was seen by CNBC.
A ground stop halts flights at their departure point. Departing traffic was halted until further notice, the agency said.
"The FAA issued a nationwide ground stop for all U.S. airports following communication issues impacting multiple Air Route Traffic Control Centers," the FAA said.
The agency said in a statement that "FAA technicians are investigating the issue."