The United States is in the process of determining what the future mix of radio-navigation should be for its users. Air, marine and land navigation requirements are being closely re-examined and the ability of future or existing systems to meet these requirements is being investigated. Events such as the destruction of Korean Airline Flight 007 have focused new attention on the Navstar Global Positioning System (GPS), both by the President and Congress. Behind the selection of a future systems mix is a planning process that has been under way for some time. The first Federal Radio-navigation Plan, published in 1980, listed two key decision points in the planning process; a joint preliminary recommendation to be made by the Departments of Defense (DOD) and Transportation (DOT) in 1983 and a national level decision in 1986 (Fig. 1). A national decision will not be made without an opportunity for user comment and international consultations.