Privatization generally means the transfer of ownership or business from the governmental organization to the private company. Recently, our society is called as a ‘Risk Society’. In this risk holding modern society, whether the government or public sector should undertake various business holds many problems. Should privatization be carried out completely in some fields? In other words, what kind of business should the government or public sector actually undertake? Would partial privatization ―usually outsourcing part of the business of the government― work? What kind of responsibility should it be if the government would partly outsource its business? The way of privatization and its application trigger many fundamental questions and issues.This paper takes up air traffic control system among many fields where privatization becomes an issue. After looking at several countries’ air traffic control systems from a viewpoint of legal system (mainly Japan, the U.S., the U.K. and Germany), it considers the nature of the system and ways of preferable controlling of the air.Air-traffic control system varies depending on the country. For example, Japan and the U.S. are keeping the governmental control of the air with full responsibility to attached to the government and air traffic controllers are in charge of business as government officials. On the other hand, the U.K and Germany have adopted the system of outsourcing the business to organizations which could be owned by the private sector and the organization is in charge of air traffic control.It is difficult to say what kind of form is appropriate to a country, because each country has its own view and its way of thinking towards risk that the government should cover. There are many views including the clarification of where responsibility lies. It is an active issue what sector should receive liability claim and how to pay compensation when an accident occurs.In this paper, as stated above, basic legal structure of air traffic control system of Japan, the U.S., the U.K. and Germany is compared from a perspective of ways of looking at the public service-what kind of business should be carried out by the government as a service by the public- in addition to a look at difference in the way of thinking about civil service system and the air traffic control system’s past, present and future perspective is examined.