While Amazon won FAA approval to fly beyond an operators' visual line of sight, "the program remains a work in progress," reports Bloomberg: 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... [S]ome 217 feet (66 meters) in the air [at a drone testing facility], 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. Not long after the incidents, Amazon paused its experimental drone flights to tweak the aircraft software but said the crashes weren't the "primary reason" for halting the program. Now, five months after the twin crashes, a more detailed explanation of what happened is starting to emerge. Faulty readings from lidar sensors made the drones think they had landed, prompting the software to shut down the propellers, according to National Transportation Safety Board documents reviewed by Bloomberg. The sensors failed after a software update made them more susceptible to being confused by rain, the NTSB said. Amazon also removed a backup sensor present that had been present on earlier iterations, according to the article — though an Amazon spokesperson said the company had found ways to replicate the removed sensors. But Bloomberg notes Amazon's drone efforts has faced "technical challenges and crashes, including one in 2021 that set a field ablaze at the company's testing facility in Pendleton, Oregon." Deliveries are currently limited to College Station, Texas, and greater Phoenix, with plans to expand to Kansas City, Missouri, the Dallas area and San Antonio, as well as the UK and Italy. Starting with a craft that looked like a hobbyist drone — and was vulnerable to even modest gusts of wind — Amazon went through dozens of designs to toughen the vehicle and ultimately make it capable of carting about 5 pounds, giving it the capability to transport items typically ordered from its warehouses. Engineers settled on a six-propeller design that takes off vertically before cruising like a plane. The first model to make regular customer deliveries, the MK27, was succeeded last year by the MK30, which flies at about 67 miles an hour and can deliver packages up to 7.5 miles from its launch point. The craft takes off, flies and lands autonomously. Read more of this story at Slashdot.