Canadian airline WestJet has introduced updated cabin interiors on select Boeing aircraft, adding three distinct seat classes and charging extra for seats that can recline.

The changes were announced by the airline on Sept. 23, and by the end of October, the first 43 refreshed Boeing 737-8 MAX and 737-800 will be available for passenger travel.

"The modern cabin experience will offer a bright, airy atmosphere with an upgraded design that features new seats, adjustable headrests and enhanced cushion and back support with a fixed recline design in Economy that helps preserve personal space," WestJet said in a press release.

Seat classes include premium, extended comfort and economy. Those wanting their seats to recline will need to book premium, and only 12 exist per plane. 

WestJet explains the changes to passengers on its website, even stating that the back of the cabin rows 20–31 offer the least amount of space. 

"WestJet has always been a pioneer in making air travel available to Canadians, largely through keeping costs low to offer affordable airfare," Samantha Taylor, WestJet Executive Vice-President and Chief Experience Officer, said in a statement. 

"The layout for our refreshed cabin caters to our guests’ diverse preferences. Whether they opt for Premium seating with extra amenities and legroom or for more affordable ticket prices with less space, we’re excited to introduce this range of products for our guests to enjoy," she said.