The study found that passengers who go from sea level up to 8,000 feet of altitude saw the oxygen content in their blood fall 4%. Although this didn't trigger full on acute mountain sickness, it did bring on what the study called "increased prevalence of discomfort after three to nine hours" of exposure.
"The research showed passengers' bodies reacted at 6,000 feet similar to that at sea level," Emery said. "So we decided to pressurize the Dreamliner at 6,000 feet."
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