A pair of Amazon.com Inc package delivery drones were flying through a light rain in mid-December when, within minutes of one another, they both committed robot suicide.

Shortly before 10am on Dec 16, the first Prime Air drone dropped its package at a dummy residence at the company’s rural Oregon testing range, then flew back to an asphalt pad to begin its landing sequence. Instead, some 217 feet (66 meters) in the air, the aircraft cut power to its six propellers, fell to the ground and was destroyed. Four minutes later and 183 feet over the taxiway, a second Prime Air drone did the same thing.