The U.S. Federal Communications Commission (FCC) is investigating a nationwide CenturyLink Inc network outage that has affected service on 911 emergency phone calls across the country, agency chairman Ajit Pai said on Friday. “The CenturyLink service outage is … completely unacceptable, and its breadth and duration are particularly troubling,” Pai said in a statement. Asked about the FCC investigation, a spokeswoman for CenturyLink said the company had been in contact with the federal agency and would cooperate fully.