Delta Air Lines has cancelled 5000 flights due to ongoing IT issues.

After suffering a major global cyberattack last week, Delta Air Lines struggled to return to normal operations on Sunday, canceling 1,250 of the 3,500 flights originally scheduled.

The issue left thousands of Delta passengers stranded across the United States, with some people having to rent cars to drive hundreds of miles and others potentially waiting days for new flights or even cancelling their trips entirely.

According to FlightAware, the Atlanta-based airline canceled a third of its flights and missed 1,700 flights (44 percent) as it worked to resolve its operational issues after a failure in its crew tracking system.

Delta has not yet published a timeline for returning to normal operations, according to a flight-tracking website, and has canceled another 305 flights on Monday. The airline has canceled more than 5,000 flights since Friday.

While other American airlines have largely returned to normal, Delta has struggled to do so. United Airlines was the second-largest airline in terms of canceled flights on Sunday, with 266 flights (9 percent) canceled.