Southwest Airlines (LUV) has shifted its policy to put unvaccinated workers on unpaid leave who have applied for religious or medical exemptions but have not received approval by the federal deadline of Dec. 8.

According to a memo obtained by CNBC from Steve Goldberg, Southwest’s senior vice president of operations and hospitality, and Julie Weber, vice president and chief people officer, Southwest will allow employees who have requested an exemption that has not been approved by Dec. 8 to continue to work for the airline.

“This is a change from what was previously communicated. Initially, we communicated that these employees would be put on unpaid leave and that is no longer the case," the memo read.

Employees must wear a mask and follow social distancing guidelines while their exemption request is being reviewed, according to the memo.

Southwest said it will continue to pay workers while it reviews their exemptions.

As a federal contractor, Southwest is subject to the Biden administration’s COVID vaccination requirements that require all government employees to be vaccinated by Dec. 8 unless they have a medical or religious exemption. On Monday, some Southwest employees demonstrated outside the company's Dallas headquarters to "stop the mandate."

American Airlines and Delta Air Lines are also federal contractors that need to abide by the federal government mandate, while United Airlines issued a companywide vaccine mandate for its employees in August.

United has said that more than 96% of its workforce is vaccinated, while Delta announced in August that unvaccinated employees would have to pay $200 more a month for company health insurance premiums, starting in November. About 90% of Delta’s 80,000 workers are reportedly vaccinated.

As of Tuesday at 11:55 a.m. ET, shares of Southwest Airlines were trading at $49.58, down $0.19, or 0.39%.

Southwest Airlines again extended the timeframe for resuming flights on the Boeing 737 MAX, this time until mid-April 2020 Southwest Airlines again extended the timeframe for resuming flights on the Boeing 737 MAX, this time until mid-April 2020 Photo: AFP / Mark RALSTON