Why is your phone in SOS mode? U.S. cell services have faced outages all morning.

Did you wake up this morning and find that your smartphone was in SOS mode?

You're not alone. There appears to be a major cell service outage across the U.S.

What's going on?

On Thursday, hundreds of thousands of smartphone users reported trouble with their cellular network. While the reason for the downtime is unclear as of publication, it's safe to say that there are currently major cell service outages nationwide.

And we do mean nationwide. Outage reports have come in from cities like Los Angeles, New York, Chicago, Houston, and Atlanta.

What cellular networks have been hit?

The outages appear to be affecting every major carrier in the U.S. 

According to DownDetector, tens of thousands of AT&T customers have reported outages, peaking at more than 73,000 reports around 9am ET. However, the issue is ongoing with thousands of new outage reports coming in each hour as of publication.

"Some of our customers are experiencing wireless service interruptions this morning," reads a statement posted on AT&T's website. "We are working urgently to restore service to them. We will provide updates here as they are available."

However, the outages are not confined to AT&T either. Thousands of Verizon and T-Mobile customers are also experiencing outages. The outages are also trickling down to smaller carriers like Boost Mobile and Cricket, which use the major carriers networks to serve their customers.

Why SOS mode?

SOS mode is a feature found in iPhone, Android devices, and other smartphones that allow users to make emergency calls when there's no cellular service available.

While the feature is a good one to have, it's also a tell that your smartphone currently isn't connected to your cellular network. This means that you can't make phone calls to your contacts, receive calls, use the internet, nor do anything else with your phone that requires a cellular connection.

Mashable will provide updates on this story as more information is known about these cellular network outages.