Customers could not make calls, text, or access the internet, and some had problems contacting the emergency services.

Although Verizon and T-Mobile customers reported some network outages, too, they seemed much less widespread. T-Mobile and Verizon said their networks were unaffected by AT&T's service outage, and customers reporting outages may have been unable to reach customers who use AT&T.

According to an anonymous industry source, the issue for the outage seems to be related to how mobile services hand over calls from one network to the next, a process known as peering. They said there was no sign that it resulted from a cyberattack or other malicious activity.

This has not stopped the internet from being flooded with conspiracy theories about how it was all a test run for a cyber campaign against all good gun-carrying born-again Christians.  Others suspected it was all to do with solar flares or a Russian EMP bomb.

The FCC said: "We are aware of the reported wireless outages, and our Public Safety and Homeland Security Bureau is actively investigating. We are in touch with AT&T and public safety authorities, including FirstNet, as well as other providers."

AT&T's network went down for many customers across the United States on Thursday morning, leaving customers unable to make calls, text or access the internet.

By a little after 3 pm ET, about 11 hours after reports of the outage first came out, the company said that it had restored service to all affected customers.

"We have restored wireless service to all our affected customers. We sincerely apologise to them," AT&T said in a statement. The company added that it is "taking steps to ensure our customers do not experience this again in the future."

On Thursday morning, more than 74,000 AT&T customers reported outages on the digital-service tracking site DownDetector, with service disruptions starting around 4 am ET.

That's not a complete number: It only tracks self-reported outages. Reports went up steadily throughout the morning but levelled off in the 9 am ET hour.

By 12:30 pm ET, the DownDetector data showed some 25,000 AT&T customers still reporting outages. By 2 pm ET, fewer than 5,000 customers were still having issues.

Earlier on Thursday, AT&T admitted that it had a widespread outage but did not give a reason for the system failure. By late morning, AT&T said most of its network was back online, and it confirmed on Thursday afternoon that service was fully restored.