An MQ-1 Predator drone takes off from Creech Air Force Base, Nev., on May 11, for a training sortie over the Nevada desert. (U.S. Air Force photo/Staff Sgt. Brian Ferguson)

An MQ-1 Predator drone that crashed about 8.6 miles northwest of Holloman Air Force Base in New Mexico in October lost its satellite communications link with its pilot before flipping over and falling out of the sky, an Air Force investigation has found.

The results of the investigation were released Thursday by the service in a 23-page report. The loss of communications with the $4.5 million unmanned aircraft was found to have “substantially contributed” to the Oct. 30 accident, the investigation found. It said the overall cause of the incident was a “commanded symmetric pitch,” but it did not determine how the aircraft was ordered to crash. The pilots and air crew were cleared of any wrongdoing.

The investigation’s release comes as the U.S. military grapples with a series of drone accidents on U.S. soil. As outlined in a recent Washington Post investigative report, there have been at least 47 military drone crashes in the United States since 2001.

The Oct. 30 MQ-1B Predator crash was the ninth drone crash at Holloman since 2001 to be classified as a Class A accident – which means, under current standards, that it resulted in at least $2 million in damage.

Five of the Class A accidents at Holloman involved QF-4E Phantom aircraft. Those drones are retrofitted F-4 fighter jets used for target practice by other planes.

The Air Force began flying Predators on training missions from Holloman on Sept. 10, 2009. Exactly one day later, a Predator crashed during takeoff and hit a fence. The cause has never been disclosed; Air Force officials chose not to convene an Accident Investigation Board, which normally examines how a crash happened and writes a publicly releasable report.

Two MQ-9 Reapers – a bigger, faster and more capable version of the Predator – crashed in Class A accidents at Holloman on Aug. 24, 2011 and Oct. 7, 2011. Unusually, the Air Force did not convene an Accident Investigation Board into those accidents, either, so the official causes were kept quiet.

On top of those accidents, another Predator crashed at Holloman on Oct. 22, 2010 in a Class B accident, which means that it caused between $500,000 and $2 million in damage. On April 2, 2011, a Reaper crashed in a Class B accident. The Air Force does not convene Accident Investigation Boards for Class B mishaps, so the official causes of those crashes are also unknown.

The results of the Oct. 30 accident investigation were released on the same day as a new report by the Stimson Center examining U.S. drone policy. It suggested that the U.S. reliance on lethal drone strikes has become a “slippery slope” toward a state of never-ending war. The Predator that crashed in New Mexico in October was unarmed at the time.

Staff writer Craig Whitlock contributed to this report.