From the Illinois State Emergency Management Agency – (SWIC) Statewide Interoperability Coordinator (communications)

Here is the official release as of now. No end time noted.

Regarding the reported overnight disruptions to cellular service, at this time, the cause of the outage is unknown and there are no indications of malicious activity. Media sources are also reporting cascading impacts from AT&T’s outage causing disruptions among other major telecommunication providers such as Verizon and US Cellular.  No official statement has been released by AT&T and CISA Central is coordinating with the Communications-ISAC to learn amplifying information and will provide updates accordingly.

Unofficial info points to a routing issue between networks and not disruptions within the other carrier networks.

AT&T/FirstNet provided this information:

GTOC Incident Number: 274934

Severity: 1-High

Location of Issue: Multiple Markets

Impact Type: Shared

Vicinities/Locations Impacted: National and surrounding areas.
Markets impacted include: Affecting all Regions and Markets Nationwide.

Users Impacted: Customers may not be able to make or receive a VoLTE call

Symptoms you MAY experience: Customers may experience no service or degraded service in the coverage area impacted

Technology: 5G, LTE, VOLTE

Start Time: Thu Feb 22 2024 02:45 CT

End Time:  Unknown

UPDATE:

Technicians are working towards resolution as quickly as possible.