Companies are delaying sending employees back on the road this fall amid another surge in coronavirus cases.

Airlines and hotels had hoped that business travel—one of the most lucrative pillars of their business—would start to bounce back in the coming months. Those hopes are fading as the busy summer travel season peters out, and the spread of the Delta variant of Covid-19 postpones some companies’ plans to return to offices and resume in-person meetings and events.

“I’d say it’s a pause, as compared to continued growth. That said, we understand why it’s paused,” Delta Air Lines Inc. DAL -1.40% Chief Executive Officer Ed Bastian said in an interview last week.

Delta said U.S. corporate travel returned to about 40% of pre-pandemic levels this summer, and the airline was predicting it would climb to 60% by September. “We won’t be at 60%,” Mr. Bastian said.

About 60% of the more than 400 business travelers who responded to a survey by Morning Consult for the American Hotel & Lodging Association said they would postpone coming trips.

Clarke Smith, an instructor for a company that provides training and consulting services for tech businesses, was set to take his first work trip last month, a few weeks after his company had started visiting clients in person again.

“Right about the time I started to get a little bit nervous is when they called and said, ‘Let’s pull the plug on this,’ ” he said.