Basic economy once ruled the airplane. Aside from those few rows in the business class cabin, what most passengers got was a bare bones, bottom-rung experience. Now, even on budget airlines, premium seating is taking over.

• American Airlines introduced a Boeing 787-9 plane this summer with redesigned premium economy seats that have headrest wings for “additional privacy,” water bottle storage, and calf and footrests. It has said it plans to expand its lie-flat and premium economy seating by 50 percent before the end of the decade.
  

• Delta expanded its premium economy service — which comes with amenities kits, meals and more legroom — to transcontinental flights last fall. Glen Hauenstein, the airline’s president, said in the company’s recent earnings call that it used segmentation of the main cabin (think fees for extra leg room) as “the template that we’re going to bring to all of our premium cabins over time.”
  
• United Airlines said in July that it would add more premium economy seats between business class and economy-plus seats on its wide-body jets. “That’s the cabin, I think, that is generating very good returns,” Andrew Nocella, the airline’s chief commercial officer, said during the company’s earnings call.