It will take more work and additional research before the FAA can draw any meaningful conclusions from a study it commissioned on the size and pitch of seats on U.S. commercial flights and potential impacts on passenger safety.

The agency in 2019 tasked its Civil Aerospace Medical Institute with carrying out experiments on seat size and pitch and aircraft cabin evacuation time trials, testing the theory that, as Americans grow physically larger on average, current seating may not just be uncomfortable but dangerous.

The CAMI report, finished in 2021, drew criticism for its methods, and a recently completed peer review from the National Academies of Sciences, Engineering, and Medicine concluded that the study fell short of the FAA’s expectations and did not generate data officials could act on.

“The findings from the review suggest that CAMI’s research project does not provide the information needed for the proposed purpose,” the peer review found. “The project’s fundamental shortcoming is that it does not directly assess how seat width and pitch interact with passenger body size variables to affect evacuation performance, and especially for plausible scenarios in which the number and concentration of people with large body sizes on a flight may differ from the pattern for the flying public generally.”

CAMI recruited a group of 775 individuals intended to represent the U.S. public and tested their ability to sit down in and stand up from different-sized seats at 28-, 32-, and 34-inch pitches. The researchers hypothesized that, as long as the test subjects were able to sit down in their seats, they should be able to get up from them and evacuate a standard aircraft cabin in good time. Part of their reasoning rested on the assumption that passengers will spend far more time queuing in a cabin’s aisles during an evacuation than actually rising from their seats.

After completing the time trials and analyzing the results, CAMI concluded that its hypothesis was correct and found that variations in seat width and pitch did not affect cabin evacuation times, even though study participants with larger body sizes did tend to evacuate more slowly.

Design Flaws

National Academies reviewers echoed earlier criticisms from the scientific community that the CAMI study did not include individuals under the age of 18, older than 60, or with physical limitations due to safety considerations. These excluded populations are part of the flying public, they said, and any test that excludes them should not be used to inform regulatory decisions.

Reviewers also faulted CAMI for failing to test body size as a variable, not using participants with larger body sizes who could have “stress tested” the experiment, and extrapolating their conclusion on seat size and pitch from the given data. The CAMI test group was not a perfect representation of actual American passengers, they noted, and a continued increase in the average size of flyers “might lead to interactions by passengers with one another and with seat dimensions that slow evacuation time, an outcome inconsistent with CAMI’s hypothesis that seat and row exit times are immaterial to evacuation flow.”

“Indeed, the committee finds that the key conclusion in CAMI’s report that current airplane seating configurations should not impede the evacuation of 99% of the general U.S. population is not supported by the design and results of the research project,” the review continued. “To make such a definitive claim, CAMI would need to undertake an extensive series of additional evacuation trials or combination of seat row exit trials and computer-based evacuation simulations that specifically take passenger body size into account as an independent variable.”

The reviewers said some useful data might be obtained from the CAMI study by applying more granular analyses and reviewing video recordings of the evacuation trials. Still, the main benefit would be informing the design of future experiments, they said.