Delta Air Lines CEO Ed Bastian has endured many business challenges since joining the company 25 years ago—from bankruptcy and job cuts to the COVID-19 pandemic. The latter impacted him in a personal way, too. Bastians’s mother died in February 2020, which he says was likely from the COVID-19 virus.

Bastian, who called his mother his personal hero, wondered what could possibly come next.

“We thought our lives were never going to return to what we had,” Bastian told Fortune’s editor-in-chief Alyson Shontell at South by Southwest’s annual conference, regarding the pandemic.

But after taking some time to grieve the loss of his mother and wrapping his head around the major changes that were going to occur globally, Bastian says the early days of the pandemic also showed him how important it is to lead during difficult moments.

“This was actually the most important time to lead in history. For our company, and candidly, for our world,” Bastian says.

“I appreciated that it was a privilege to lead, it was not a burden. And that gave me strength every single morning to get up and to go lead and put that brave face on.”

In 2020, Delta hired the Mayo Clinic to advise on cleaning protocols, ventilation practices, and in-air social distancing. Then in 2021, the airline created the chief health officer role—the first of its kind—and Bastian personally brought on Henry Ting, whose job was to simply protect employees and passengers.

Under Ting’s leadership, Delta implemented science-backed protocols with the Delta CareStandard, which still includes frequent wipe-downs of surfaces both in airports and on board, disinfection procedures that have been certified by Lysol, and readily available hand sanitizer dispensers. HEPA air filters on board Delta flights also work to remove 99.99% of particles, including viruses.

From April 2020 to April 2021, Delta also blocked the purchase and use of middle seats to facilitate social-distancing on board. Many of the COVID-19 safety protocols Delta implemented, as well as their transparency regarding the protocols, paved the way for other airlines.

“I think everyone in this environment needs to ensure they’re staying very, very close to their people, they’re communicating, that there’s a level of transparency about what’s happening, and never more so than their travel experience,” Bastian told the Harvard Business Review in 2022.

“It’s never more important to be visible and let people know what you know and what you don’t know. We tell people what we need them to know and do, and when they ask us, we give them our very, very best insight as to how we see the future and what’s happening around and why we do make some of the decisions that we’ve had,” he says.

Bastian didn’t downplay the weight of being a leader, though. He says it’s definitely hard, and there are times you may not feel like being at the helm, but having an unrelenting commitment to succeed and seeing the fruits of your labor makes it worth it.

Despite the pandemic’s harsh impact on the travel industry (among many others), Bastian remembered Delta’s business model, which he says is “to bring the world together, not to separate.” That pushed them to continue working toward business goals, no matter how dismal everything seemed at the time.

“The world needed to be together, so that’s why I knew we were going to get there,” he says. That doesn’t mean it came easy.

The COVID-19 pandemic led to Delta’s revenue plummeting, down 66% in 2020 from the year prior. Before that, Delta experienced continued revenue growth between 2003 and 2019. Now, Delta Air Lines is the most profitable airline in the world, with almost $50.6 billion in operating revenue in 2022.

Delta emphasizes the impact their employees have on the success of the company. Just last month, Delta paid out $1.4 billion in profit sharing to employees, equal to about 10% of their annual pay.

Per the Delta website, their strong 2023 earning and profit-sharing payout “are the direct result of the exceptional work and commitment of Delta’s people throughout a challenging operational year.”

Bastian also mentioned the pride he has in Delta employees during his SXSW interview. Despite many companies performing mass layoffs during the pandemic, he says Delta didn’t lay off a single employee.

“I think that was our biggest statement of who we are,” Bastian says.