The expert in airline-reward programs noted that carriers have dropped prices for premium cabins since the pandemic, as people continue to forego business trips in favor of working from home and Zoom meetings.

Cheaper fares have attracted leisure travelers, who are more sensitive to price hikes than people expensing trips on a company credit card.

"Once you get consumers used to buying $4,000 round-trip business class pretty easily all summer long, it's a lot harder to all of a sudden move that up to $7,000 where you were, because consumers get locked in and then they'll say, 'well, I'm not going to go,'" Kelly said.

On the other hand, passengers paid up for premium economy or business to avoid being "jammed in like a sardine" during the pandemic, he said, especially as fares plunged during lockdowns as people stayed off planes.

"So consumers started to get a real good taste of life in the front of the plane and realized … economy sucks," Kelly said. "Once you start flying first class, it's really hard to go back."

Beating the system

Kelly shared two travel hacks. The first is to stockpile transferable credit card points accepted by multiple airlines. When you fly, you can use them to make a back-up reservation on a different airline that allows last-minute cancellation with no penalties.

"If my original flight goes out, I cancel, and I get all my miles in cash back, zero fees," Kelly said. "You can use your points as insurance policies to make sure you're getting where you want to go."

The second is to take advantage of cheaper reward programs in other countries, for example by exchanging credit-card points for Air France points instead of Delta ones.

"In France, they don't have 100,000-point offers, bonanzas like we do here," Kelly said. The result is reward flights overseas haven't risen in price as quickly as in the the US.

"Cause if they did that in France, where their French members can't earn points like we do, there would be a riot," Kelly said.