A minimum airplane seat width of 18 inches improves passenger sleep quality by 53% when compared to the 1950s 17-inch standard, according to a study by The London Sleep Centre. The study recorded sleep measurements via polysomnography. “The difference was significant. All passengers experienced a deeper, less disturbed, and longer night’s sleep in the 18-inch seat,” Dr Irshaad Ebrahim, MBChB MRCPsych, of The London Sleep Centre says in a release. “They went from one sleep stage to the next as you would expect them to do under normal circumstances. Whilst, in the narrower 17-inch seat, the passengers were affected by numerous disturbances during sleep—which meant they rarely experienced deep restorative sleep. When it comes to flying long haul in economy, an inch makes a huge difference on passenger comfort.”

This was a cross-over study to assess the impact on sleep variables by two different seat sizes—17 and 18 inches in a small sample of six healthy adults who had been previously screened for the presence of medical and sleep disorders. The cabin environment was structured to simulate as close as possible the true flight environment from the start including lighting to replicate sunset and sunrise, aircraft take-off and background sounds, in-flight entertainment, and catering.

Airplane maker Airbus released a statement saying it promotes 18 inches as the standard seat width for future long-haul economy air travel. Kevin Keniston, Airbus’ Head of Passenger Comfort, says in a statement: “If the aviation industry doesn’t take a stand right now, then we risk jeopardising passenger comfort into 2045 and beyond, especially if you take into account aircraft delivery timetables combined with expected years in service. Which means another generation of passengers will be consigned to seats which are based on outdated standards.”