A U.S. Air Force contractor who accidentally walked into the propeller of a MQ-9A drone on a California airfield was improperly trained and disoriented before the fatal misstep, a military investigation released Friday concluded.

Stephanie Cosme, 32, was working as a contracted civilian test engineer at Gray Butte Airfield on Sept. 7, 2023 when she unintentionally walked into the propeller during a ground test.

The Palmdale resident was airlifted to Antelope Valley Hospital in Lancaster, but died a short time later from severe injuries.

An Air Force Materiel Command Accident Investigation Board on Friday released a report attributing the deadly error to two main causes.

Firstly, Cosme was improperly instructed or trained on taking telemetry readings while approaching the MQ-9A with the engine running, the report found.

Secondly, she experienced a loss of situational awareness while moving around the aircraft to take those readings, investigators found.

AIB President Brig. Gen. Lance R. French also highlighted two additional factors that contributed to the tragedy: a lack of clear communication between the contractor test team and ground support personnel, and a rush in the tests due to previous delays and cancellations.

The AIB report recreated the accident scenario with an MQ-9 parked in the same spot, engine running, and similar lighting conditions as on Sept. 7. 

During the simulation, the spinning propeller was not visible when viewed from the rear of the aircraft, the direction from which Cosme approached.

Cosme worked for Sumaria Systems, LLC, and was providing test support services for the Air Force Life Cycle Management Center, Detachment 3.