The Federal Communications Commission has released a staff report detailing the causes and impact of a nationwide T-Mobile outage that occurred in June.

“T-Mobile’s outage was a failure,” said FCC Chairman Ajit Pai.

T-Mobile did not follow several established network reliability best practices that could have either prevented the outage or at least mitigated its impact, FCC said.

Neville Ray is the chief technology officer of T-Mobile.

“All telecommunications providers must ensure they are adhering to relevant industry best practices, and I encourage network reliability standards bodies to apply their expertise to the issues identified in this report for further study,” Ajit Pai said.

T-Mobile on June 15, 2020 experienced an outage on its wireless networks that lasted over twelve hours, disrupting calling and texting services nationwide, including 911 service, as well as access to data service in some areas.

In today’s report, the FCC’s Public Safety and Homeland Security Bureau estimates that at least 41 percent of all calls on T-Mobile’s network failed during the outage, including at least 23,621 failed calls to 911.

FCC notes that T-Mobile’s outage was caused by an equipment failure and exacerbated by a network routing misconfiguration. The outage was also magnified by a software flaw in T-Mobile’s network that had been latent for months and interfered with customers’ ability to initiate or receive voice calls during the outage.

T-Mobile works with both Ericsson and Nokia to run its network.

FCC said it plans to release a Public Notice, based on its analysis and other recent outages, reminding companies of industry-accepted best practices.