Mike Boyd, president of aviation forecasting and consulting firm Boyd Group International, projects that traffic could dip between 4%-5% by the end of September.
"Universally, our forecasts are showing that after Labor Day, traffic is going to flatten a lot more than we thought," Boyd told FOX Business.
This dip, according to Boyd, is due to uncertainty regarding whether virus-related restrictions will be reinstated. It's similar to what happened when air travel first plummeted to historic lows in 2020, he said.
"The uncertainty … wasn't so much the health uncertainty," he said. "It was a worry [that] if you got to Omaha, would the entire town be shut down and you can't buy a hamburger?"
Now, "people are saying, 'I might want to visit grandma, but I'm not sure whether we're going to shut down the state or not. Let's put it off again,'" he added.
Uncertainty, according to Boyd, is the very thing that "kills air transportation."
"And we're getting more and more uncertainty day by day," he said.
Member operations specialist Willis Orlando of Scott's Cheap Flights, which monitors air travel, agrees, saying concerns over the delta variant have already "put the brakes on the serious momentum towards a return to pre-pandemic interest in flying, both internationally and domestically."
"Over the last month or so, as concerns over the delta variant have grown, this steady increase in demand has tapered off," Orlando told FOX Business in a statement.
Domestic flight searches are down about 20% compared to 2019 and international searches are down about 40%, according to Orlando.
If this trend continues over the next several weeks or months, Orlando said consumers should expect to see even cheaper flights to popular leisure destinations such as Cancún and Los Cabos in Mexico.
"Airlines have already begun rapidly adding back capacity that they’d cut in 2020. With more planes in the sky, but a slower increase in demand, the best way to fill those empty seats will be by cutting prices," Orlando said.
However, Boyd pointed out that "what appears on the TV screens every night" will dictate how long this trend will last.
"If it's constant stories about the delta variant spreading or this happening or that happening, all of it negative or more face masks … as long as that continues, air transportation demand will decline," Boyd said.