A pilot crashed an MQ-9A Reaper at the Nevada Test and Training Range last year after becoming distracted by checklist procedures and missing warning signs of a stall, the Air Force said Thursday.

According to an accident investigation board report released by Air Combat Command, the Reaper — which was assigned to the 432nd Wing at Creech Air Force Base in Nevada — took off under the control of a launch and recovery element on June 7. After reaching the cruising altitude of 8,500 feet, the launch and recovery crew started handing control of the Reaper over to the crew that was meant to fly it on the training mission.

However, after receiving control of the Reaper, the pilot set its power too low to maintain level flight, the report said. Because the pilot was distracted by handover checklist procedures, the pilot didn't notice the stall warnings at first. By the time the pilot tried to increase the power to recover, it was too late, and the Reaper crashed about two minutes after the handover. The $11.1 million Reaper was destroyed on impact. There were no injuries, fatalities or damage to private property.

The report said that the pilot's "misprioritization" — or focus on completing the checklist and failure to notice the warning signs and act to correct the stall in time — was the primary cause of the accident. 

"I started to realize the plane was stalling while I was in the other [handover] checklist procedures," the report quotes the pilot as saying. "At that moment in time I was prioritizing the [handover] checklist."

The crew's loss of situational awareness and failure to realize they had accepted the handoff of the Reaper at about 500 feet below the preset altitude substantially contributed to the crash, the report said.

The crew didn't realize the Reaper was climbing to reach the preset 9,000-foot altitude, and instead thought it was ascending on its own, according to the report. The pilot switched from autopilot to manual, or landing configuration, which disables stall protection and automatic adjustments to airspeed and altitude, and helped lead to the crash.