In Croatia, car, train, ship, and plane transportation are the primary modes of transportation. For long-distance travel, road transport consists of a comprehensive network of state, county, and local routes supplemented by a highway network. Sea transport, which is based on the ports of Rijeka, Ploe, Split, and Zadar, and river transport, which is based on the Sava, Danube, and, to a lesser extent, Drava, are the two types of water transportation. Croatia is home to nine international airports and a number of airlines, the most well-known of which are Croatia Airlines and Trade Air. Although the rail network is fairly developed, buses tend to be used more frequently than trains for intercity travel.