next day air rates refer to the cost of shipping an item via an expedited service that guarantees delivery by the following business day. Companies like UPS, FedEx, and DHL offer next-day air services to ensure quick delivery for time-sensitive shipments. The rates depend on the size, weight, and destination of the package, with higher costs typically associated with heavier or more distant shipments. Next-day air is an ideal choice for urgent deliveries that require fast and reliable service.