Breaking with United Airline’s vaccine mandate of get vaccinated or get fired, Southwest Airlines, American Airlines and Delta Air Lines say they will not require unvaccinated workers to get vaccinated. Delta says that 75% of its workforce is already vaccinated without a companywide mandate. All three airlines say that while they will not mandate their employees to get vaccinated, they will encourage it. Delta and United have said that all new hires are required to be vaccinated.
See "3 major airlines are choosing not to mandate COVID-19 vaccinations for workers", Pete Muntean, CNN, August 11, 2021