Southwest Airlines has scrapped a plan to put unvaccinated employees who have applied for but haven’t received a religious or medical exemption on unpaid leave starting by a federal deadline in December.United Airlines implemented its own vaccine mandate in August, a month before the government rules were announced. Southwest Airlines and American Airlines are among the carriers that are federal contractors and subject to a Biden administration requirement their employees are vaccinated against Covid-19 by Dec. 8 unless they are exempt for medical or religious reasons.