AT&T experienced a software glitch on Tuesday, causing a wireless service disruption for some users, including difficulties with 911 calls. The outage, which began in the afternoon and peaked in the evening, impacted several major cities, but was not nationwide. AT&T has since resolved the issue, apologizing for the inconvenience. The outage comes at a time when AT&T is reporting positive financial results, adding new wireless customers and maintaining its popularity among dividend investors.