Delta Air Lines halted US flights because of a technology failure, the second major domestic US airline to ground services due to computer glitches in only a week. Delta’s international flights are exempt from the grounding, which was caused by “automation issues,” the FAA said. "Our systems are down," Delta said in a tweet. "The IT department is working to rectify the situation as soon as possible," said the airline. United Continental last week had to ground its US flights following a computer failure. While that outage resulted in relatively few cancellations, it lasted about 2.5 hours. Last year, a rash of computer failures disrupted flight operations at US airlines. Thousands of passengers were stranded as carriers struggled to keep older information systems working. <br/>