The Trans-Mongolian Railway, about 1,496 km (930 mi) in length, connects Mongolia with both China and Russia. Ulaanbaatar has been connected to the Trans-Siberian Railway via Bayantümen since 1939 and via Sühbaatar since 1950, and to the Chinese Railways via Dzamïn üüd since the end of 1955. Choybalsan is also connected to the Trans-Siberian system via Ereenstav. Ulaanbaatar Railways has been linked to Nalayh since 1938 and to Darhan and Tamsagbulag since 1964. The Sharïn Gol Open-Pit Coal Mining Industry was connected to the Darhan industrial center during the third five-year plan (1961–65) by a 60-km (37-mi) rail line. A 200-km (124-mi) railroad line connects Erdenet, a copper-molybdenum mining and industrial center near the Russian border, with the Trans-Mongolian Railway. The total length of railroads in 2002 was 1,815 km (1,128 mi).
Mongolia had about 3,387 km (2,105 mi) of roadways in 2002, of which 1,563 km (972 mi) were paved. Freight and passenger traffic are carried on the Selenge River and across Hövsgöl Lake.
There were 34 airports in 2001, of which 8 had paved runways. Mongolia's first air service began operating between Ulaanbaatar and Verkhneudinsk in eastern Siberia in 1926. Miat-Air Mongol is the principal airline. In 2001, 255,300 passengers were carried on scheduled domestic and international airline flights.