"Inside ground-control stations, drone pilots sit with binders of checklists that guide them through every conceivable scenario. But costly errors are still easy to make. One recurring mistake: forgetting to turn on the Stability Augmentation System, which prevents the drone from going wobbly or into a spin. In at least five cases, pilots did not switch it on, or accidentally switched it off, then sat perplexed as the aircraft went into a nose dive."