Thousands of Delta Air Lines customers, stranded for hours Monday, can blame larger And more sophisticated airline computer systems, along with increased consolidation of air carriers. The Atlanta-based carrier reported a computer outage early Monday that caused more than 650 flights to be canceled and more than 2,000 to be delayed. By the end of the day, the system was back online but the ripple of delays continued. “I apologize for the challenges this has created for you with your travel experience,” Delta Chief Executive Ed Bastian said in a video statement posted on the airline’s website. “The Delta team is working very, very hard to restore and get these systems back as quickly as possible.” Several computer applications were affected, including the company’s website. Delta initially said the problem was caused by a power outage in Atlanta. A spokesman for Georgia Power, however, said the outage was limited to Delta’s Atlanta systems And was caused by the failure of the airline’s equipment. Computer-related cancellations and delays have become more common in the past few years as airlines increasingly rely on larger More complicated computer systems that are tied into airport kiosks And smartphone apps, according to airline experts. Because of industry consolidation in the last decade A shutdown at any of the major carriers now has a bigger effect on travelers Particularly at hub airports dominated by one airline. The nation’s four biggest carriers — American Airlines Delta, Southwest Airlines and United Airlines — carry nearly 80% of the country’s domestic air travelers.