United Airlines’ employees who are granted exemptions to a company vaccinate mandate for religious reasons will be put on temporary unpaid leave starting next month, the airline told staff Wednesday, citing the recent rise in Covid cases.

The airline last month said its 67,000-person U.S. workforce must be vaccinated against Covid-19 this fall, but said it would consider exemptions for religious and personal beliefs as well as medical reasons.

Airlines’ approaches to encourage vaccination rates of their staff have varied. Delta Air Lines is imposing a $200 surcharge on unvaccinated employees’ company health care premiums. Delta, American Airlines and Alaska Airlines will end pay protections for unvaccinated employees who contract or are exposed to Covid-19.

United said Wednesday if an employee’s request for a religious exemption is denied, they must be vaccinated within five weeks of the denial notice and get the first shot by Sept. 27, or they will be terminated.

Pilots, flight attendants, gate agents and airport customer service agents who interact with customers who are granted those exemptions can return to work “once the pandemic meaningfully recedes,” United said, without specifying the timeframe.

Other employees like mechanics and dispatchers granted exemptions can return to work after the airline puts in new testing and other measures, the carrier said in a staff note. It is still determining safety measures for office workers with exemptions and whether they need to come in at all.

Staff who are given medical exemptions for not getting the vaccine will be put on temporary medical leave.