United Airlines is warning thousands of employees that their jobs are at risk

United Airlines said the jobs of about 14,000 workers are at risk when a second round of federal aid ends this spring, the latest sign of how the industry is struggling to regain a foothold in the coronavirus pandemic.

Companies are required by law to notify employees in advance if their jobs are at risk and that does not mean they will eventually lose their jobs. United is turning to new voluntary measures to reduce the workforce.

United and American Airlines recently began recalling thousands of workers they left when the first round of government payroll came to an end in the fall. Congress approved additional support for the industry last year, on the condition that they recall workers’ leave and keep payrolls up to March 31. United told workers last year that the recalls would likely be temporary.

“Despite ongoing efforts to distribute vaccines, customer demand hasn’t changed much since we took those workers back,” the airline said in a staff note seen by CNBC on Friday. “When the recalls began, United said most of the recalled employees would return to their previous status as a result of the fall leave around April 1.”