Thinner seats on airplanes are becoming more and more prevalent as airlines seek out ways to increase revenue. Southwest, United, and Alaska Airlines are among carriers that have added another row of five to six seats on some of their aircraft. This allows the airlines to save more on fuel (as thinner seats weigh less) and carry more paying passengers. Generally, seats are one inch closer together than they previously were. Airlines say the seats are just as comfortable and that passengers won’t notice, although some have begged to differ. Alaska Airlines will replace all of its seats by the end of 2014, but will also install power outlets for its customers. However, plane manufacturer Airbus recently chastised airlines with regards to this trend, citing research that more comfortable seats improves sleep quality for passengers by as much as 53%.