United Airlines and its pilots’ union have reached an agreement to prohibit the airline from mandating COVID-19 vaccinations to its pilots.

The Air Line Pilots Association confirmed the two parties have reached the agreement.

“Since the COVID vaccination is not mandatory, pilots who elect not to be vaccinated will not be subject to any discipline,” the agreement states.

United’s CEO, Scott Kirby, has told workers at a meeting in January that the company may make the vaccine mandatory for employees and urged other companies to do the same.

The agreement between the airline and the union also adds that those pilots who have been vaccinated would be eligible for extra pay.

What are other airlines doing?

Delta Air Lines announced earlier this month that it would require all new hires in the United States to be vaccinated against the COVID-19 virus.

American Airlines confirmed in January that it had no plans to make the vaccine mandatory for its workers.

While private U.S. companies can require employees to get vaccinated against COVID-19, experts say they could put themselves at risk of legal and cultural backlash if they do so.