Why a Civilian Defense Employee Died After a C-17 Test Flight Last Year

The Air Force blamed the death of a 33-year-old Missile Defense Agency civilian employee after a C-17 test flight in August on decompression sickness complicated by his underlying medical conditions, including obesity, hypertension, an enlarged heart, and cardiovascular disease, according to the results of an accident investigation board released April 12.

However, the report leaves several questions unanswered, such as how the employee was cleared for the flight, why medical specialists aboard did not recognize his symptoms, and why the test flight continued as planned, even after it was clear he was experiencing a medical emergency.

The C-17 took off from Joint Base Elmendorf-Richardson at about 10 a.m. on August 21, flying over the Pacific Ocean past the Aleutian Islands. The MDA employee was there to help test out a simulated high-altitude, medium range ballistic missile launch. Following procedure, the crew donned helmets and oxygen masks to start pre-breathing pure oxygen 30 minutes before the test to prevent decompression sickness.

At about 2 p.m., the crew opened the C-17 cargo doors, conducted the test, then closed the doors after about five minutes and repressurized the jet. But after the doors closed, the MDA employee began sweating excessively and making “motions of distress,” the report wrote. Crew members flagged down High Altitude Airdrop Mission Support (HAAMS) physiological technicians, who oversee crew safety on un-pressurized high altitude flights. Barely able to breath, the MDA employee used a whiteboard to communicate, but he could only scribble illegibly, the report said. He also indicated pain and a lack of mobility in his right arm.

All of those symptoms indicate decompression sickness, investigation board president Brig. Gen. Derek Salmi noted in the report. Also known as “the bends,” decompression sickness is when changing air pressure forms nitrogen bubbles in the body that can pressure nerves, damage tissue, and block blood flow. The procedure for decompression sickness is to put the patient on pure oxygen, descend to normal air pressure, land immediately at the closest airfield, and, if necessary, put the patient in a hyperbaric oxygen therapy chamber.

But the HAAMS technicians failed to recognize the symptoms of decompression sickness and instead treated the patient for hyperventilation. They placed him on an emergency oxygen mask as the aircraft cabin altitude decreased below 10,000 feet, where oxygen masks are not required. One of the HAAMS technicians thought the employee was stable and removed his mask, but his right arm was “droopy,” he had difficult standing up and “looked like a guy that had been drinking all night,” according to a crew member.

The crew notified the pilot but said the MDA employee was in a stable condition, then moved him to the floor near the front of the aircraft. The flight deck trusted the HAAMS techs to care for the ill employee and provide updates, but it is unclear how often those updates were delivered, and the patient continued to slur his words, breath heavy, appear in pain, and look pale. The mission was planned for seven-hour duration, and the flight landed at 5:00 p.m. as originally scheduled without any indication of rushing to land.

The instructor pilot recalled feeling shocked at seeing the MDA employee’s condition for the first time, saying he “looked like he had a stroke,” and did not appear stable. Doctors at a nearby hospital said he needed a hyperbaric chamber, but the nearest one was in Seattle and air transport would not be available until the next morning.

Over the next 12 hours, the patient’s blood pressure dropped, and his lungs, liver, and kidneys failed. Despite the physicians’ best efforts, the employee went into cardiac arrest at 8:06 the next morning and was pronounced dead 26 minutes later.


Salmi said the initial misdiagnosis “likely delayed available treatment measures such as continued oxygen use … as well as descent by the aircraft to a lower cabin altitude.” Another problem was the lack of follow-up care during the return flight “despite the persistent and significant symptoms” exhibited by the MDA employee.

Even so, the general said the employee’s case of decompression sickness, combined with his underlying conditions, was so severe that the outcome may have been the same. The report cited a history of hypertension, an enlarged heart, and blockage of the coronary arteries as contributing factors. How was an employee with such conditions allowed on the flight?

The MDA employee had a current Federal Aviation Administration Class III physical, “the simplest medical certificate for private, recreational, and student pilots to obtain,” according to Flying Magazine. He had been flying high-altitude test airdrop missions for a little over a year, and the August 21st sortie was his sixth such mission. In fact, he was considered “an expert in this mission set … and was actively instructing another MDA colleague as part of the mission.”

Even had he been in better shape, the employee may still have developed decompression sickness: Salmi wrote that recent medical studies found a 30 percent chance for anyone taking part in high-altitude operations to develop some symptoms, ranging from mild to severe. The Air Force did not respond before publication to a question of whether anyone was held accountable as a result of the report.

Earlier this month, the Air Force released an investigation into the death of a contractor who was killed last year when she walked into the moving propeller of an MQ-9 during ground tests. The death was blamed on a confluence of factors, including inadequate training, poor lighting, noisy conditions, and a rush to finish testing, all of which contributed to the victim’s loss of situational awareness while she took telemetry readings.

The deaths of the two civilians helped make fiscal year 2023 a difficult year for aviation accidents. Air Force Times reported two deaths, 10 aircraft destroyed, and 75 major non-combat aviation mishaps in total: a five-year high. Those mishaps occur as maintainers and aircrew try to meet mission requirements with a dwindling number of aging aircraft.

Meanwhile, the Air Force is recalculating its approach to risk as the service adopts agile combat employment (ACE), concept where small teams of Airmen launch and recover aircraft at remote or austere airfields, then relocate to avoid being targeted by enemy missiles. Many Airmen expect to carry out those operations without support and without connection to higher command. On April 2, the Air Force Safety Center unveiled a new plan to keep pace. Part of the plan is to use machine learning models to review safety data and provide better analysis for safety officers to improve their processes.

“Mishap reporting data is a lagging indicator and limited tool,” the center wrote in a release. “Our intent is to develop analytical tools to assist commanders with proactive risk reduction, mishap prevention, and maximized readiness.”