Will business travel ever be the same?

When will it resume in full? That seems to be anyone's guess, though estimates stretch as far as 2025.

The emergence of the delta variant, uncertainty around border restrictions and the slow rollout of vaccinations to some parts of the world are variables that make it tough to predict when the old patterns of work travel will return, if ever.

In recent earnings calls, Delta and American said domestic business travel had reached 40 and 45 percent, respectively, of 2019 levels by June. Even with the business recovery fairly muted, the number of passengers at Transportation Security Administration checkpoints was up significantly compared to 2020, nearing or topping 2 million almost every day of the past month.

But while it may be fine for a traveler to jet off to Hawaii or Mexico for a pleasure trip, it is trickier for a company to send an employee off into the pandemic.

"Businesses are much more risk averse," said Suzanne Neufang, chief executive of the Global Business Travel Association.

Another issue, she said: Where would those travelers go?

"With so many offices not completely open, there's no place to meet," she said. "You can have coffee, but it's hard to show a PowerPoint in a coffee shop."

Experts say the return to office life, expected in the fall, will spur more business travel. But it is unclear whether the delta-variant-fueled surge in coronavirus cases will widely delay that comeback. Already, major corporations such as Apple, Google, Twitter and Uber have delayed their back-to-office plans.

Tori Emerson Barnes, executive vice president of public affairs and policy at the U.S. Travel Association, said the variant has added some uncertainty and anxiety to the outlook. The trade group's forecast predicts that business travel will reach only about half of 2019 levels by the end of this year.

Another stumbling block: Restrictions keep many would-be business travelers out of important markets - especially the United States. The country is still closed to travelers from many countries, including China, India, Brazil, the United Kingdom, Ireland and nations in the European Schengen area.

"Definitely government restrictions are the biggest barrier at this point in time," said Paul Abbott, CEO of American Express Global Business Travel, which manages business travel, meetings and events for clients around the world. He said the company has seen numbers soar in places where the virus is well under control and workers can move about freely.

"Where travel is permitted and restrictions have been removed and there is trust and confidence in the processes, travel is returning in significant numbers and there's very strong demand," he said.

Steve Hafner, CEO of the travel search company Kayak - which launched a corporate travel tool earlier this year - said continued mask requirements and recommendations are also working against a return to business trips.

"No one wants to wear a mask on a plane for a long trip. No one wants to wear a mask in an office either," he said. "As long as masking is out there, I think that's going to be a head wind for business travel."

Both the U.S. Travel Association and Global Business Travel Association have predicted a full recovery by 2025. A recent report from professional services firm Deloitte projects U.S. corporate travel could reach a "new normal" of about 80 percent of pre-pandemic levels by the end of next year.

Bill Gates predicted that 50 percent of business travel would go away. An analysis by the Wall Street Journal was more generous, estimating that between 19 and 36 percent of business trips by air are likely to never return.

"I think this variant has done nothing more than to exacerbate the existing situation, which in my mind will never be the same as it was pre-COVID," said Robert Quigley, senior vice president and global medical director at International SOS, a medical and travel security firm. "It opened up our collective eyes to the idea that maybe we don't need to be constantly traveling. Maybe we can Zoom."

Those who are already traveling for work say their trips are meeting the needs that teleconferencing tools like Zoom just can't.

Christine Choi, a New York-based partner at investment firm M13, travels to Los Angeles quarterly or every other month to meet with team members, welcome new colleagues and see product demonstrations. She said being on Zoom meetings 12 hours a day reminded her how important face-to-face interaction was to get to know people and learn what they need.

"It's hard to expect humans to lean so dramatically on the digital experience and the screen experience," she said.

Abbott said companies also realize they might need to get more workers on the road for competitive reasons.

"It's all very well saying, 'Could we continue to exist on Zoom?' Yes," he said. "But is the objective of your company 'We want to continue to exist' or is it 'We want to grow, we want to win, we want to acquire new clients'?"

Still, even the biggest promoters of business travel acknowledge that the experience will be different, from the types of trips that people take to the length and frequency.

Abbott said he believes there will be a more dispersed workforce in the future, which means those spread-out employees will need to get together.

"That will absolutely create more business travel," he said.

Neufang, of the Global Business Travel Association, said the group has been emphasizing "the right travel in the right way." She said some companies are linking their business travel comeback to new sustainability goals - for example, cutting back on single-day jaunts in favor of fewer but longer trips.

"Fewer takeoffs and landings: That is better for the planet," she said.

Describing himself as an optimist, Hafner said he expects business travel to eventually surpass 2019 levels. But, he predicted, he expects to see "a lot fewer day trips and hopefully a lot more 'bleisure'" - or the combining of leisure and business, sometimes with a partner or family.

"Now you know you can work from anywhere. Why make it a day trip?" he said. "Go more days."

Choi said she has extended her trips as she navigates covid-era necessities like trying to avoid layovers, choosing hotels with outdoor spaces for meetings and implementing activities like outside coffees and walks into her visits.

"My trips are getting slightly longer because I want to make it worth the strange travel," she said. "The complexities makes me want to pack as much into my visits as possible."