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United Airlines customers with flights booked to travel during the government shutdown will be eligible for a refund, CEO Scott Kirby told employees in a memo on Wednesday. The news came after the Federal Aviation Administration and Department of Transportation announced a reduction in schedules across 40 domestic airports, starting on Friday, as a result of the shutdown. "[A]ny customer traveling during this period is eligible for a refund if they do not wish to fly – even if their flight isn't impacted. That includes non-refundable tickets and those customers with basic economy tickets," Kirby said in the memo. He added that the airline's "long-haul international flying and our hub-to-hub flying will not be impacted by this schedule reduction direction from the FAA." "Instead, we will focus our schedule reductions on regional flying and domestic mainline flights that do not travel between our hubs," Kirby said, adding that the airline will utilize its app, website and push notifications to stay in touch with customers about flight changes and to offer rebooking options. Transportation Secretary Sean Duffy told "Fox & Friends" on Thursday that the decision to limit air travel capacity to 40 airports was "data-driven." "We ere seeing increased pressure in these 40 markets. And we looked at the data — this was data driven — and so taking 10% of the flights out will reduce that pressure, which is what we want to do," Duffy said. "Now, does that mean there's going to be no delays? No, Brian," Duffy told Fox News' Brian Kilmeade. "There's potentially still going to be delays if we have staffing triggers, and we don't have enough controllers in an aerospace where we did cut 10%, you might see additional delays." As of 9:00 a.m. ET on Thursday, 825 flights within, into or out of the U.S. had been delayed while 42 had been canceled, according to FlightAware.com. When asked about whether Americans should consider canceling their holiday plans, Duffy said it was "hard to predict" what could happen in the coming weeks, pointing to the historically long government shutdown.