An aerial photographer and his assistant on April 1, 1997, climbed to almost 28,000 feet in an unpressurized Cessna 337D Skymaster that had been modified to carry a through-the-floor camera. They were “on oxygen,” of course, breathing through face masks. The assistant remembers the pilot reaching back to turn on the oxygen tank valve; she felt the flow of cool air into her mask and noted that the indicator in the oxygen line had flipped from red to green, indicating a positive flow. As the Cessna climbed through 20,000 feet, however, she felt dizzy and disoriented, and she closed her eyes—the last thing she remembers about the flight. Air Traffic Control was unable to contact the pilot, though its radar painted the airplane climbing through its assigned altitude—FL250—and reaching 27,700 feet, then descending rapidly to 26,000 before disappearing from the scope about 15 miles west of Pittsburgh, Pa. The Cessna had come apart because of the extreme stresses of an uncontrolled high-speed spiral dive, with a pilot dead of hypoxia at the controls. Through a horrible April Fool’s Day mix-up, the airplane’s portable oxygen tank had been filled with ordinary compressed air, not oxygen—fine for scuba divers, fatal for pilots. Shedding its left outboard wing, tail booms and empennage, the four-seat cabin, a pod about the size of a subcompact car, fell nearly five miles and ended up in a tree on a golf resort. With the right wing remaining and the cabin and two engines at one end of it, again a maple-seed spiral almost certainly slowed the descent. The woman in the right seat survived with minor cuts and bruises, apparently having been better acclimated than the pilot to flying at Everest altitudes while breathing what was essentially ambient air.
