Saying that “Make no mistake – we’re still in the early miles of this marathon,” Delta Air Lines Chief Executive Officer Ed Bastian and his peers in the airline industry are hoping for the best but planning for the worst when it comes to the coronavirus pandemic.

U.S. airlines expect it will be years before their business recovers from COVID-19, according to Alison Sider of the Wall Street Journal, even after pulling together over $100 billion by tapping government aid and mortgaging assets including planes and frequent-flier programs.

Recapturing demand for travel due to the virus has been difficult for airlines, although they passed an important milestone on Sunday. Carriers have said they likely have enough cash to withstand a prolonged downturn. But passenger demand will be depressed for years, Bastian and United CEO Scott Kirby said.

“While the pandemic is the worst crisis in the history of aviation, it also has presented us with opportunity,” United Chief Executive Officer Scott Kirby and President Brett Hart wrote Friday in a memo to the airline’s corporate officers.

United and Delta together lost $16.8 billion in the first nine months of the year. Both have shrunk their workforces by at least 20 percent. U.S carriers hope to stop the bleeding by getting a second round of government aid, as Congress continues to work on a stimulus package.

But another issue remains – removing travel restrictions and quarantines in most destinations that are also prohibiting people from traveling.

“We’re literally looking at where people want to go next week,” Joe Esposito, Delta’s senior vice president of network planning, said at an industry event this week.