Southwest Airlines will cancel 1,500 daily flights starting Friday, an increase from what the Dallas-based airline said several days prior as demand for air travel plummets even more.

Southwest Airlines Co. (NYSE: LUV) flies about 4,000 flights a day normally, meaning the cancellations represent nearly 40 percent of the airline's daily service.

"We'll implement the cancellations on a rolling, multiple-day basis to provide customers with advance notice of changes and alternate flight options," a Southwest spokesperson said in a statement.

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In addition to the cancellation increase, the carrier is also looking at adjusting its Hawaii service, according to an internal memo viewed by the Dallas Business Journal.

Alterations to Southwest's Hawaii schedule shows how quickly circumstances are changing for airlines as they grapple with the new industry realities COVID-19 has brought on. Southwest President Tom Nealon told the Honolulu Star-Advertiser earlier this month the carrier's Hawaii flights would be immune to schedule cuts.

However, Hawaii Gov. David Ige said over the weekend people coming to Hawaii, residents and visitors alike, will be ordered to stay in a 14-day period of self-quarantine starting Thursday.

"Southwest is preparing to revise our near-term flight schedule of Hawaii service and is working through new protocols for our employees and our customers arriving in Hawaii after this new order takes effect," Cetta Larabee, director of Inflight Crew Scheduling and Crew Ops Support, said in the memo. "These arrival protocols and procedures are not finalized yet, and we will share more as soon as we can."

Larabee added that the company considers flights between the islands essential to Hawaii residents looking to travel from one island to another. Demand will wane for those flights, too, she said, adding that more information is to come.

The uptick in cancellations comes just days after Southwest announced it was canceling 1,000 daily flights starting this past Sunday. The carrier had previously planned to slash capacity by at least 20 percent between April 14 and June 5.

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