United Airlines CEO Scott Kirby called upon the Trump administration and Congress to restart critical negotiations on coronavirus aid in a letter released Friday. Kirby cited substantial layoffs if the current aid package is not extended.

"We recognize the severe impact the virus is having on our entire economy and the need for support touches many other individuals, organizations and programs,” Kirby said in the letter, which was also signed by the leaders of five unions. “Assistance now can help to lessen the long-term impact to the economy and ultimately speed recovery.”

Kirby calls for the extension of aid from the Payroll Support Program for airline employees, part of the CARES Act signed in March to provide coronavirus aid. Aid recipients like United Airlines were barred from furloughing employees until Oct. 1. Now facing that deadline without an extension could result in a substantial loss in employees for United.

“Without additional funding for the PSP grants, up to 16,000 members of the United family are at risk of involuntary furloughs beginning October 1st. Continuation of this critical program would prevent the furloughs and provide additional time for the industry to reach recovery without losing our colleagues to involuntary furloughs,” union leaders wrote.

Some of the unions who signed the letter included the Airline Division International Brotherhood of Teamsters, United Airlines Master Executive Council and the Association of Flight Attendants–CWA.

Kirby’s letter comes after a letter Wednesday from American Airlines CEO Doug Parker, who along with other airline industry unions, asked for the same aid extension.