Air transport industry, which has a presence in Columbus, includes commercial air carriers that transport the customers to and from national as well as international destinations, either based of specific routes or "charter", which is a customized route for a customer or a group of customers. The carriers can be either mainline or regional in scope of operations, with the former also flying on international routes. This industry comprises professionals of various kinds with specialized functions, such as pilots and flight attendants (the most visible part of this industry), as well as ground staff that includes management personnel as well as travel agents. Specific sectors in the industry that employ personnel include reservation and transportation ticket agents, gate or station agents, and aircraft mechanics and service technicians. Another segment of this industry is the air cargo segment, whereby goods are transported via airlines from one place to another. Passenger aircraft have both full service and budget options for customers. The working hours may be irregular as flights operate during the night as well. Since flying an aircraft is an act that requires considerable skill and expertise, pilots have to compulsorily take rest between duty shifts to ensure safe transport. Air transport remains one of the most popular means of transport in the country, growing at an average annual rate of 4%.