AT&T outage: Key things to know after thousands lose service nationwide

An AT&T network outage on Thursday caused tens of thousands of cell phone customers to lose service for hours, resulting in the inability to make and receive calls, send text messages, and for some, even calling for emergency services. 

The carrier is the country's largest, with more than 240 million subscribers. 

Here’s what AT&T said caused the outage, how government officials responded, and more things to know:

AT&T outage yesterday: How many people lost service? 

AT&T's outages began at about 3:30 a.m. ET, according to, and the number peaked at around 73,000.

By about noon ET, AT&T had more than 58,000 outages, DownDetector’s website showed.

Customers appeared to be impacted across the country, including in major U.S. cities like New York, Los Angeles, Atlanta, Houston, Dallas, Chicago, and Philadelphia. 

RELATED: AT&T outage: How to communicate when networks go down

By 9 p.m. ET, the reports on AT&T's network were fewer than 1,000.

Cricket Wireless, which is owned by AT&T, had more than 9,000 outages at one point but the reports had also tailed off later in the afternoon.

Users of other carriers, including Verizon and T-Mobile, also reported issues, but those companies said their networks were operating normally, and the problems were likely stemming from customers trying to connect to AT&T users.

What was the cause? 

FILE - A cellular tower is seen on Feb. 22, 2024, in Los Angeles, California. (Photo by Eric Thayer/Getty Images)

FILE - A cellular tower is seen on Feb. 22, 2024, in Los Angeles, California. (Photo by Eric Thayer/Getty Images)

AT&T said the hours-long outage appeared to be the result of a technical error, and not a malicious attack.

Specifically, the carrier blamed the incident on an error in coding.

"Based on our initial review, we believe that today’s outage was caused by the application and execution of an incorrect process used as we were expanding our network, not a cyber attack," the Dallas-based company said.

RELATED: AT&T outage: What works, and what doesn’t, without cell service on your phone 

iPhone users see SOS messages

During the outage, some iPhone users saw SOS messages displayed in the status bar on their cellphones. 

The message indicates that the device is having trouble connecting to their cellular provider’s network, but it can make emergency calls through other carrier networks, according to Apple Support.

However, many reported being unable to dial 911 on Thursday  – prompting sheriff departments nationwide to share alternative information on how to call in for emergency services.

How did the US government respond?

The Federal Communications Commission contacted AT&T about the outage and the Department of Homeland Security and FBI were also looking into it, National Security Council spokesman John Kirby said.

The FBI acknowledged it had been in touch with AT&T.

 "Should we learn of any malicious activity we will respond accordingly," the agency said.

Politicians on Capitol Hill also raised concerns over Thursday's outage. 

"We are working to assess today’s disruption in order to gain a complete understanding of what went wrong and what can be done to prevent future incidents like this from occurring," said a statement issued by Cathy McMorris Rodgers, a Washington Republican who chairs the House Energy and Commerce Committee, and Ohio Republican Bob Latta, chair of the Communications and Technology Subcommittee.

This story was reported from Cincinnati. The Associated Press contributed.