Southwest is redoing the interiors of its jets, replacing the seat cushions with thinner foam materials while keeping most of the same frames and swapping out bulky seat-back pockets for mesh. The thinner cushions are actually more comfortable, Southwest says, and even though the airline is adding one more row of seats to its Boeing 737s, passengers will get the same usable space. Seat pitch – the space allotted to each row, including the seat and legroom — will drop to 31 inches from 32 inches.

Slim seats can be comfortable and beneficial for both airlines and passengers. With slimmer seat cushions, airlines have a choice of whether to leave the same number of seats on planes and give the extra space not taken up by thicker cushions to passengers, or whether to keep the extra space for the airline by stuffing in more rows. Most airlines, needing to bolster their finances, opt for more seats over more space. Southwest 737-700s will go to 143 seats from 137 seats.

Southwest said it is also reducing the amount of recline in its seats to just two inches of travel at the top of the seat from three inches. That’s a change many travelers welcome because it lessens the intrusion on the person sitting behind you. The new seats are also lighter weight, reducing weight on each 737 by 635 pounds, which Southwest said will save $10 million a year in cost savings, mostly from reduced fuel burn. The seats also have more under-seat room for carry-on luggage

Southwest said its new interior design uses environmentally friendly recycled carpet and a brighter color scheme. Southwest will begin retrofitting its current fleet of 372 737-700s in March, with completion expected by the end of next year. Total cost will be about $60 million, the airline said. Southwest also expects to retrofit the interiors of AirTran Airways jets.