The FAA issues a nationwide ground stop for all US airports following "communication issues impacting multiple Air Route Traffic Control Centers" (Alex Fitzpatrick/Axios)

Alex Fitzpatrick / Axios:
The FAA issues a nationwide ground stop for all US airports following “communication issues impacting multiple Air Route Traffic Control Centers”  —  The FAA issued an extremely rare nationwide ground stop at all airports due to “extraordinary circumstances” and “reasons of safety.”