July 22 (Reuters) - Delta Air Lines ( DAL ) canceled

more than 600 flights on Monday, as the U.S. air carrier

continued to struggle to restore operations after last week's

global cyber outage, even as other airlines were recovering from

the incident.

About 16% of Delta's flights had been canceled as of 7:00

a.m. EST, according to data from FlightAware, out of roughly

1,100 flights to or from the United States overall, the web site

said.

The issue has stranded thousands of Delta travelers 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 is battling operational issues

after the outage hit its crew tracking system. Delta's total

number of canceled flights since Friday has exceeded 5,000.

A Delta spokesperson did not immediately respond to an

emailed request for comment.

A software update by global cybersecurity firm CrowdStrike ( CRWD )

triggered system problems for Microsoft ( MSFT )

customers, including many airlines, on Friday.

Although other U.S. airlines have largely recovered, Delta

has struggled to return to normal. American Airlines had

called off 1% of its flights on Monday, while United Airlines

canceled less than 1%.

Delta shares were little changed in premarket trading on

Monday.

Delta CEO Ed Bastian said over the weekend that the

CrowdStrike ( CRWD ) issue affected its Microsoft Windows systems,

snarling a critical application.

"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

over the weekend, according to an official, reminding him of the

carrier's responsibilities to customers and the department's

enforcement role.

CrowdStrike ( CRWD ) said a significant number of the 8.5 million

affected Microsoft ( MSFT ) devices were back online.