Decreased oxygen tension In passenger jets at cruising altitude, with aircraft cabins typically pressurized to 6, 000 to 8, 000 feet (1830 to 2440-m) above sea level, the partial pressure of oxygen is about 25% less than at sea level, which, because of the oxygen-hemoglobin dissociation curve (see figure), represents a drop in arterial oxygen saturation of only about 4.4%.