Hypoxia is a medical condition of oxygen deprivation or altitude sickness. It can adversely affect human judgement and movement at high altitudes with symptoms ranging from light dizziness to unconsciousness, even death at the extreme level. It was a principal reason for the engineering of pressurised aircrafts.

Two Virginia-based Raptor pilots became whistleblowers in May 2012 when they voiced their concerns about the F-22's oxygen problems on national television. They complained about hypoxia symptoms during and post flying the Raptor soon after the U.S. Air Force installed charcoal philtres to hedge against oxygen contamination on the fighters.