Tens of thousands of U.S. customers from Verizon, T-Mobile, and AT&T are complaining Thursday morning about the lack of wireless service or interruptions to service.

Both outgoing and incoming calls appear to be impacted, including to the 911 emergency service in some parts of the country.

A nationwide outage

According to data from problem tracking site Downdetector more than 73,000 AT&T customers from multiple states - including North Carolina, Louisiana, Texas, and Florida, reported a lack of service.

The San Francisco Fire Department published a "cell phone service outage" announcement saying that "AT&T wireless customers can't make or receive any phone calls (including to 911), although the 911 center is operational.

Network services provider Cloudflare notes today that AT&T recorded significant data loss in traffic (Mobile IPv6 and IPv4) starting 08:48 UTC, affecting AT&T subscribers in multiple U.S. cities (e.g. Dallas, Chicago, Los Angeles). 

Cloudflare data shows "that AT&T (AS7018) traffic dropped as much as 45%, compared with the previous week, in Chicago at 09:00 UTC. And 18% at the same time in Dallas."

Other AT&T users in California, Massachusetts, Michigan, Minnesota, and South Carolina, say that they have no mobile service.

It appears that some users were able to place or receive calls when connected to a WiFi network, with the WiFi-calling option enabled.

A banner on AT&T's forum informs that the company is "aware of an outage currently impacting our Mobility users and are working to resolve it ASAP."

An AT&T representative explained that service interruptions this morning are affecting some of its customers and that the company is "working urgently to restore service to them." 

"We encourage the use of Wi-Fi calling until service is restored" 

by AT&T spokesperson

Downdetector shows other cellular carriers also experienced problems over the past 24 hours, based on user reports for other providers, e.g. Verizon, T-Mobile, Cricket Wireless, Consumer Cellular, US Cellular, Straight Talk Wireless, and FirstNet.

Verizon responded to a customer that its network was working normally. The company confirmed this adding that "some customers experienced issues this morning when calling or texting with customers served by another carrier."

The Verizon spokesperson said that the company keeps monitoring the situation.

In a reply, T-Mobile said that it's network is not affected by an outage or other issues today and that Downdetector "is likely reflecting challenges our customers were having attempting to connect to users on other networks."

The cause of the outages remains unclear at the time of publishing. In some cases, users said they couldn't place calls regardless of the recipient's network.