uschools/iStockBy MINA KAJI and AMANDA MAILE, ABC News

(WASHINGTON) -- A group of 16 Senate Republicans expressed their support for an extension of the $25 billion payroll support program (PSP) for United States airlines Wednesday, as the demand for air travel remains suppressed and tens of thousands of airline employees face potential furloughs and layoffs.

In October, U.S. carriers are expected to lay off employees when they are no longer tied to the conditions set forth by Congress to receive federal aid.

"In recent weeks several airlines have notified significant segments of their workforces that their jobs could be at risk on October 1, 2020, following the expiration of CARES Act relief," the senators wrote to Senate Majority Leader Mitch McConnell and Senate Minority Leader Chuck Schumer.

United Airlines and American Airlines have already announced they are preparing to furlough up to 36,000 and 25,000 employees, respectively, due to lack of business amid the coronavirus pandemic.

Executives from Southwest Airlines, Delta Air Lines and JetBlue, on the other hand, have been more optimistic about the possibility of avoiding involuntary layoffs, at least in the short term, due to a large number of employees accepting early retirement offers and buyouts.

The senators' letter follows calls from over 200 House members for an extension of the PSP that they say would help preserve airline jobs until the spring of 2021.

The program "saved hundreds of thousands of frontline airline workers' jobs—and not a penny went to the airlines themselves or their shareholders," the representatives wrote.

In an interview with the Washington Post, Delta Air Lines CEO Ed Bastian said he would support a "clean extension" of the PSP for another six months.

"The CARES Act was incredibly successful in that it gave airlines six months, post the pandemic start, to be able to have a plan to deal with the pandemic," Bastian said.

Air travel is still down around 75% compared to last year and unions representing those on the front lines have also been vocal advocates of more federal aid.

"Congress provided critically needed financial aid to the airlines at the outset of this pandemic for the purpose of preventing hundreds of thousands of layoffs," Capt. Joe DePete, the Air Line Pilots Association president, said. "Unless we all act now, this aid, and the strong labor protections attached to it, will expire October 1—even though the virus is not under control and the travel industry remains devastated."

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