Some traffic must fly at night in order to meet today's business needs. Companies like FedEx and UPS rely on night flight and are an essential part of our fast-paced business environment that guarantees overnight delivery to satisfy the needs of customers. Some traffic flies later at night in order to compensate for time differences in other parts of the world. Airports in the U.S. are required to be open 24 hours a day and cannot restrict operations due to federal law.