Delta Airlines struggles to recover from the global IT glitch that affected the world on Friday, it has cancelled an additional 1,555 flights.

Although other airlines have largely recovered from the glitch, Delta has yet to give a timetable for the resumption of normal operation and has also cancelled 1,250 on Sunday and another 305 flights for Monday.

Between last Friday and Saturday, Delta cancelled 3,500 flights following the hard hit on technology worldwide.

According to Financial Times, the issue has stranded thousands of Delta travellers across the United States, with some having to rent cars to drive hundreds of miles while others could have to wait days for new flights or cancel trips altogether.

The Atlanta-based airline, which cancelled a third of its schedule and delayed another 1,700 flights or 44 per cent, according to FlightAware, is battling operational issues after the outage hit its crew tracking system.

Delta has offered no timetable for the resumption of normal operations and has already cancelled another 305 flights for Monday, the flight tracking website said. Its total of cancelled flights since Friday now stands at more than 5,000.

Delta CEO Ed Bastian said the issue affected its Microsoft Windows systems, snarling a critical application.

“In particular, one of our crew tracking-related tools was affected and unable to effectively process the unprecedented number of changes triggered by the system shutdown,” Bastian told customers in an email.

In a separate note, he told employees that Delta would continue to “tactically adjust” schedules to ensure safety.

Transportation Secretary, Pete Buttigieg, spoke with Bastian, according to an official, reminding him of the carrier’s responsibilities to customers and the department’s enforcement role.