ABSTRACTthere has been recent concernwithin the government about the “proliferation of radio navigation systems.” Today, the prime domestic civil air navigation system (VOR/DME) is essentially only usable by aviation due to line–of–sight restrictions. With the availability of wider coverage systems, and low cost microprocessor based user equipment, it may be possible to consolidate air, marine, and land navigation services into one system to be operated by the government. However, each of these services has its own peculiar requirements.The purpose of this paper is to evaluate the feasibility of introducing other navigation systems into the VOR/DME system environment. In particular, two of the most promising systems, LORAN–C and NAVSTAR–GPS, are considered. The issues that are addressed concern the distribution of costs between the users and government, distribution of costs among the various classes of users, user amortization of VOR/DME equipment, signal–in–space redundancy requirements, relationships to landing and communications airborne equipment, and satisfaction of operational requirements. Future implementation scenarios are outlined and subjected to economic analysis. One of the main conclusions drawn from the economic analysis is that a reasonable transition plan to either LORAN–C or NAVSTAR–GPS, if they are successful, would be to accommodate the more high performance users with these systems, and retain only the VOR part of the VOR/DME system for service to lowe