That, of course, was not how many people around the U.S. responded to the rollout of vaccine mandates at companies and for federal employees.

But Kirby says he and the rest of his management team were “open, honest, and transparent about communicating with our team that it was 100% about safety.” That led to 99.7% of employees getting vaccinated within eight weeks.

“It has become actually a point of pride for the people of United Airlines, rather than being controversial. In some ways [it’s] been transformative to the kind of culture that we want to have going forward at United,” Kirby says.

As for the other .3%?

“Well, the .3%, unfortunately, are going to be leaving United Airlines and moving on to some other career,” he says. “When we say safety is our number-one core value, we mean it. We don’t compromise on safety. We don’t compromise on any safety initiatives.”

Kirby joins Fortune cohosts Ellen McGirt and Alan Murray on Leadership Next, a podcast about the changing rules of business leadership, to talk about the vaccine mandate and running an airline in the age of COVID-19, pandemic travel, and sustainability. Listen to the full episode below.