The Federal Communications Commission (FCC) said wireless major AT&T decided to pay $5.25 million to settle a U.S. investigation after two outages in 2017 prevented about 15,000 callers from making emergency 911 calls.

FCC said the 911 service outages were the result of planned network changes implemented by AT&T inadvertently interfering with the company’s routing of 911 calls.

FCC said the March 2017 outage lasted about five hours, resulting in the failure of 911 calls from some 12,600 unique users, while the May 2017 outage lasted 47 minutes, resulting in 2,600 failed 911 calls.

FCC said during the March outage the company failed to quickly, clearly, and fully notify all affected 911 call centers.

AT&T said it cooperated with the review and agreed that providing access to emergency 911 services is critically important.

Several other carriers agreed to settlements after an April 2014 outage affected 11 million telephone users.

Verizon Communications agreed to a $3.4 million fine after a six-hour 911 outage in April 2014 that affected about 750,000 wireless consumers in nine California counties.

CenturyLink agreed to a $16 million settlement in the April 2014 outage.

FCC said the outages at the carriers in April 2014 resulted in 6,600 missed 911 calls about domestic violence, assault, motor vehicle accidents, a heart attack, an overdose, and an intruder breaking into a residence.

T Mobile US agreed to a $17.5 million settlement after two 911 service outages nationwide in August 2014. The separate but related outages lasted approximately three hours and affected almost all of T-Mobile’s then 50 million customers.

FCC said the April 2014 outage was the result of a preventable software coding error at a call management center in Colorado.