ATLANTA (NewsNation Now) — Delta Air Lines has managed to avoid furloughs but is now asking more employees to take unpaid leaves of absence, a sign of the deepening slump in air travel as coronavirus cases increase across the United States.

CEO Ed Bastian said Wednesday that Delta will need takers for its unpaid-leave program “for the foreseeable future.”

“I ask everyone to consider whether a voluntary leave makes sense for you and your family,” he said in a memo to employees.

With revenue down sharply, Delta expects to lose up to $12 million a day on average during the fourth quarter.

Unlike American Airlines and United Airlines, which furloughed a combined 32,000 workers in October, Atlanta-based Delta avoided furloughs by convincing thousands of workers to retire early or take unpaid leave.

Southwest Airlines also has avoided furloughs, but last week the Dallas-based carrier warned nearly 7,000 workers that they could lose their jobs if unions don’t accept pay cuts.

Last week, Delta announced it was partnering with the CDC to become the first airline to launch coronavirus contact tracing for travelers arriving in the United States. The voluntary contact tracing program is set to begin Dec. 15.

Delta also said it will continue to block the middle seats of their planes to allow for better social distancing until March 30, 2021.

Passenger traffic rose over Thanksgiving week, although numbers were down more than half from a year earlier. Traffic has dropped since the holiday.

Only 501,513 people passed through U.S. airports on Tuesday — 74% lower than the same Tuesday a year ago, the sharpest percentage decline since Sept. 15. The seven-day rolling average of passengers has been falling for nearly two weeks.