On the night Stephanie Cosme died, her sister and brother said they received a curt explanation from a U.S. Air Force official who met them at the hospital: The civilian contractor was failing to follow protocol when she was hit by an aircraft’s rotating propeller and killed.

The family would wait eight agonizing months to find out more about how the accident unfolded during relatively low-risk ground testing on a MQ-9A Reaper drone at Gray Butte Airfield near Palmdale, California on Sept. 7, 2023. They felt sure there was more to the story than Cosme, a 32-year-old testing engineer who worked for Air Force contractor Sumaria Systems, LLC, simply not following instructions.