Traditionally, Bhutan's communications have been mostly with Tibet, through several strategic mountain passes. Most travelers continue to journey on foot or mounted on hardy ponies bred to withstand great altitudes and steep slopes. Goods are transported by porters or on pack animals. Many of the rivers are still crossed by native cantilever bridges of excellent construction.
Prior to the 1961–66 development plan, there were no surfaced roads in Bhutan. Since then, a network of roads and suspension bridges has been built by India. In 2002, there were about 3,285 km (2041 mi) of roads, including about 1,994 km (1,239 mi) of surfaced roads. Of the 186 suspension bridges projected in the 1981-87 economic plan, 102 were completed by 1985. There is bus service linking Paro Dzong and Tashi Gang Dzong with Indian border towns. In 2001 there were 2 airports, only 1 of which had a paved runway. The national air carrier, Druk Airlines, began operations in 1983 with regular flights between Calcutta and Paro Dzong, the site of Bhutan's main airfield. In 2001, 35,100 passengers were carried on scheduled domestic and international flights.