About 2,000 United workers have requested an exemption on medical or religious grounds, the company said Tuesday, the day after the vaccine mandate deadline took effect for about 67,000 U.S.-based employees. The airline plans to assess those requests by Oct. 15, the same day employees granted exemptions will face being put on unpaid leave.

Chief Executive Officer Scott Kirby announced the vaccine policy on Aug. 6 as a safety measure to protect staff and customers.

“This was an incredibly difficult decision but keeping our team safe has always been our first priority,” Kirby and United President Brett Hart said in a memo. “The most effective way to keep our people safe, is to make sure they’re vaccinated.”

U.S. President Joe Biden was scheduled to meet with Kirby Wednesday in Chicago ahead of an event related to his push for U.S. companies to require employee vaccinations. But Biden’s trip to Chicago was called off, the carrier said.

Last week, six United employees sued the carrier in federal court in Fort Worth, Texas, alleging the mandate violates laws offering religious and disability accommodations in the workplace. The airline’s policy offers no alternative for mask wearing, periodic testing or social distancing, the workers said.