The US has a single form of interstate rail provider, Amtrak, with 44 routes on 21,000 miles of track. The publicly funded railway provides an alternative to flying or private vehicle with tracks spanning the country. 46 of SO states are serviced, but rail is limited by the sheer size of the nation. Cross-country trips are prohibitively lengthy, and can take days, compared to air travel. Though interstate rail service is of great benefit and has even greater potential, it is not today a fully viable travel option in most areas.