July 24 (Reuters) - Delta Air Lines ( DAL ) reported

sharply fewer cancellations Wednesday as the U.S. airline looks

to return to normal after cancelling more than 6,000 flights

since Friday.

The Atlanta-based carrier said as of 6:30 a.m. ET (1030 GMT)

it had canceled just 47 flights - only 1% of its flights -

compared with 511 on Tuesday and 1,160 on Monday. Delta said

late Tuesday it was "seeing solid day-over-day progress across

operating metrics that the entire team should be proud of".

A software update by global cybersecurity firm CrowdStrike ( CRWD )

triggered system problems for Microsoft ( MSFT )

customers, including many airlines, on Friday. But disruptions

at other major U.S. carriers had largely subsided after Friday

but persisted at Delta.

The U.S. Transportation Department opened an investigation

Tuesday into the massive Delta disruptions that impacted more

than 500,000 passengers and stranded people across the United

States.

Transportation Secretary Pete Buttigieg said the

investigation is focused on "how this breakdown could have

happened, and how it could be that days after the other airlines

are back to normal" as well Delta customer service resources.

"We require a basic level of customer service," he added.

The issue has left customers fuming. Many complained they

waited hours for assistance as the airline's helplines were

overwhelmed. Some were forced to rent cars, driving hundreds of

miles to get to destinations, while others said they would have

to wait days for new flights.

Representative Rick Larsen, the top Democrat on the House

Transportation Committee, said he will introduce legislation to

boost the operational resiliency of airlines in the near future.

"The slow response by some airlines to this meltdown has been

unacceptable," Larsen said.

Senate Commerce Committee chair Maria Cantwell said she is

concerned Delta is not complying with passenger rights

obligations under a new law.

In December, Southwest Airlines ( LUV ) agreed to a

record-setting $140 million civil penalty over the 2022 holiday

meltdown that led to 16,900 flight cancellations and stranded 2

million passengers, resolving a USDOT investigation.