As of 2002, a single east-west rail line of 370 km (230 mi) went from Issyk-kul' across the Chuskaya region into Kazakhstan. There were some 30,300 km (18,828 mi) of highways, of which 22,600 km (14,044 mi) were paved in 2002. Irregular service with public transportation occurs frequently. As a landlocked nation, water transportation is of minor importance with only 600 km (372 mi) of waterways as of 1990. However, inland travel is possible on several east-west rivers. Kyrgyzstan has 50 airports and airfields, of which 4 have paved runways, as of 2001. The principal airport is Manas, located at Bishkek. In 2001, 192,100 passengers were carried on scheduled domestic and international airline flights.