July 22 (Reuters) -

Delta Air Lines ( DAL ) continued to struggle to restore its

operations on Monday, three days after a

global cyber outage

snarled flights around the world, stranding thousands of

customers across the country.

The Atlanta-based airline had canceled 778 flights, or

about 20% of the scheduled total as of 1:30 p.m. EST on Monday,

according to data from FlightAware. It accounted for about half

of total flight cancellations.

The company's shares were down about 2% at $44.58 in

mid-day trade. By contrast, disruptions at other major U.S.

carriers had largely subsided.

A software update by global cybersecurity firm

CrowdStrike ( CRWD ) triggered system problems for Microsoft ( MSFT )

customers, including many airlines, on Friday.

A Delta spokesperson did not immediately respond to

requests for comment.

Delta CEO Ed Bastian said over the weekend the outage

affected one of its crew tracking tools and the airline was

"unable to effectively process the unprecedented number of

changes triggered by the system shutdown."

In a separate note, he told employees that Delta would

continue to "tactically adjust" schedules to ensure safety.

Delta is widely respected for running a reliable operation.

Analysts say its on-time performance in terms of arrivals and

departures has helped the airline cement its position as a

premium airline.

Since the outage, it has canceled nearly 30% of its

flights, according to global aviation analytics firm Cirium.

The issue has left customers fuming. Many complained

that they had to wait hours for assistance as the airline's

helplines were overwhelmed. Some were forced to rent cars to

drive hundreds of miles, while others said they would have to

wait days for new flights.

"I was very disappointed in the way Delta handled this,"

wrote Bob Pearlman on LinkedIn, who had booked a flight from

Honolulu to Salt Lake City.

Bastian said the outage hit the airline on "the busiest

travel weekend of the summer," limiting its re-accommodation

capabilities.

In a staff memo seen by Reuters, Delta said it is "doing

everything possible" to bring stability to its staffing. It has

boosted incentive pay for pilots and flight attendants.

"The single biggest thing you can do to help at this

point is to pick up trips in any base," it said in the memo, a

request for crew to volunteer for extra trips.

Transportation Secretary Pete Buttigieg said on Sunday

his office had received hundreds of complaints about Delta's

customer service and asked the airline to provide prompt

refunds, free rebooking and timely reimbursements to customers.

"No one should be stranded at an airport overnight or

stuck on hold for hours waiting to talk to a customer service

agent," he said.