At a GNC warehouse in Whitestown, Indiana, workers see and hear four drones overhead every day as they complete tasks that few humans want to do: count and track full boxes of products across more than 2,000 pallets in the warehouse's aisles. The drones' regular flights allow GNC, a nutritional manufacturing company, to obtain a full view of its 250,000-square-foot reserve inventory once a month rather than once a quarter, said Bill Monk, GNC's vice president of distribution.