"Slim-line" seats, with thinner seat-back cushions, are increasingly popular with US airlines because they weigh less and help squeeze more passengers into a plane.
But the seats may not be so popular with passengers.
A new survey by the travel website TripAdvisor shows that many passengers who have tried slim-line seats are not fans.
In the survey of 1391 travellers, the website found that nearly half weren't sure whether they had sat in slim-line seats. But of those who said they had tried the seats, 83 per cent said they were less comfortable than traditional seats, eight per cent said the slim-line seats were more comfortable, and nine percent said they couldn't tell the difference.
Delta Air Lines is the latest of several major carriers to announce plans to install slim-line seats. Delta spokesman Paul Skrbec said the TripAdvisor survey was lacking because it didn't ask passengers which airlines they flew when they tried the seats. The airline's internal surveys show passengers like Delta's slim-line seats, he said.
United, Alaska, Southwest and Spirit are among the other major airlines that have installed slimmer, lighter seats in the last few years. American Airlines has also indicated it will install slim-line seats on some aircraft.
At United, internal passenger surveys show that the slim-line seats get higher ratings several months after being installed, suggesting the seats get more comfortable over time, airline spokesman Rahsaan Johnson said.
Among the critics of cramped cabins is Senator John McCain, who fired off a tweet last week about his flight to Washington from Phoenix.
"Are you as frustrated as I am that the airlines keep moving the rows of seats closer and closer together?" he said.