For example, the US government assumes transportation to be critical to the country's general economic prosperity. As such, it has sometimes been the policy of the US government to protect major US companies responsible for transportation (aircraft manufacturers, train companies, automobile companies, etc.) from failure by subsidies and low-interest loans. Such companies, among others, are deemed "too big to fail" because their goods and services are considered by the government to be constant universal necessities in maintaining the nation's welfare and often, indirectly, its security.