Do you need to be vaccinated to fly delta airlines

"It's very difficult for us to come in and mandate a vaccine that isn't even federally approved yet, the authorization hasn't been final yet, so stay tuned," Bastian said on "Squawk Box."

"We're continuing to encourage as much as we can amongst our own people and our customers to get vaccinated. The numbers are picking up" on vaccinations, he said.

More and more staff and customers have recently gotten their Covid shots as the delta variant, first discovered in India, became the dominant strain in the U.S., Bastian said.

He added that 73% of the airline's staff is fully vaccinated.

Many companies are debating whether they should implement vaccination mandates or solely incentivize more of their staff and customers to get vaccinated. The discussion has intensified as the more contagious delta variant continues to infect the largely unvaccinated areas of the United States, causing the seven-day average daily case count to recently surpass last summer's peak.

However, Bastian said Delta's flights were more than 90% full over the weekend as people are "learning how to manage and live" with the coronavirus pandemic. He said the airline carries millions of people each week, the vast majority of whom are vaccinated and fully masked.

The Transportation Security Administration in the spring extended a federal mask mandate for air, train and bus travel to mid-September, a measure that will likely be extended, barring a sharp drop in infection rates.

The travel industry was hit particularly by the pandemic, with travel restrictions aimed at curbing the spread of the virus heavily impacting demand and bookings. Domestic carriers lost more than $35 billion last year.

Since January, the U.S. government requires travelers, including citizens, show proof of a recent negative Covid test before entering the United States. Some nations require proof of vaccination to enter the country or avoid quarantine.

"I expect as those borders continue to open, you're going to see more and more of those requirements. Here in the U.S., I don't think it's necessary," Bastian said.

Delta and United Airlinesare also requiring proof of vaccination for new hires. Delta, United and American Airlines have offered extra time off or pay to employees who are vaccinated, joining big employers like Walmartthat have taken similar measures.

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Spirit AirlinesCEO Ted Christie told CNBC that the carrier is urging all passengers and employees to get Covid shots and use facial coverings, despite the low-cost carrier having no plans to implement vaccine requirements.

Back in January, United CEO Scott Kirby said the carrier was considering a Covid vaccine mandate for the entire company's workforce. The airline has so far not mandated the vaccine for all employees.