They may arrive at the same destination, but two passengers on the same flight can have strikingly different travel experiences.

One traveler breezes through a priority security lane and heads straight to an invite-only lounge for craft cocktails and a chef-prepared meal before boarding early. A flight attendant offering a glass of champagne and a warm hand towel welcomes the passenger to a spacious seat at the front of the plane.

The other traveler stands in a line at every step — security screening, a cafe selling $16 sandwiches, a crowded gate — then boards with one of the final groups, hoping there’s still room for a carry-on in the overhead bin before folding into a cramped middle seat. After the cabin lights dim, sleep comes in fragments, and a travel pillow does little to ease a stiff neck.

The contrasting journeys are no accident. Since the COVID-19 pandemic, the largest U.S. airlines have pulled out all the stops to court premium passengers who are willing to pay for comfort, convenience and exclusivity. Budget-conscious travelers may notice a widening gap between the back of the plane and up front as the carriers increasingly build their businesses around selling first-class, business-class and premium-economy seats.

“We can’t win by trying to provide the cheapest. We have to be able to win by providing the best,” Delta Air Lines CEO Ed Bastian said in a recent Fortune podcast interview.

The strategy embraced by Delta and rivals American Airlines and United Airlines marks a notable evolution for an industry that spent decades making air travel more accessible. Now, the nation’s largest carriers are reconfiguring aircraft to expand premium seating, designing new fleets with larger premium cabins and investing billions in amenities that extend the top-tier travel treatment beyond their jetliners.

But United CEO Scott Kirby has pushed back on the idea that the industry has become solely focused on chasing big spenders. He said United’s premium investments are part of a broader strategy to boost the experience of every traveler, pointing to initiatives such as seatback entertainment and improvements to the airline’s mobile app.

“We’re investing nose to tail for all customers,” Kirby said last month on financial firm Morgan Stanley’s Exceptional Leaders podcast.

The premium playbook didn’t emerge overnight.

Airlines used to fill empty first-class seats mainly by giving their most loyal frequent flyers free upgrades. Delta rewrote the rules in the early 2010s by using sophisticated pricing tools to offer more of those seats to coach passengers who were willing to pay a little more, said Henry Harteveldt, president of travel advisory firm Atmosphere Research Group.

The strategy unlocked demand airlines hadn’t fully recognized, encouraging more travelers to trade up and laying the groundwork for today’s broader premium push.

“Travelers could and would pay for noticeably more comfort, noticeably better service, noticeably more amenities, if the price was right,” Harteveldt said.

Then came the pandemic. When business travel collapsed and Zoom replaced many corporate trips, airline analysts wondered whether carriers would once again have to lure travelers with cheap fares. Instead, eager leisure travelers proved willing to splurge on premium seats and perks, convincing airlines that demand extended well beyond the traditional business road warrior, Harteveldt said.

Analysts say premium cabins — a category that expanded with the introduction of premium economy seats featuring more legroom and amenities at a fraction of the cost — now generate a disproportionate share of airline revenue compared with the space they take up on commercial aircraft.