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Current systems of instrument approach guidance, even with recent and forthcoming improvements, are shown to be inadequate for future operational needs. The potential weaknesses of current techniques include restrictions on flight-control maneuverability, limited landing rates, special terrain and siting requirements, and deterioration of service in the critical low-altitude region near touchdown. A broad look at future requirements, especially those posed by jet operations, leads to a specific set of desirable system characteristics. An approach system that is suitable to replace the interim improvements now being implemented must provide a wide enough selection of flight paths to allow versatility in flight-control techniques; it must guide aircraft to actual landings; it must be fail-safe; and it must impose minimum burdens in terms of airborne equipment and of real estate. A review of possible data sources and devices for use in an ultimate system reveals only a few promising contenders. A proposed multiangular system of minimum complexity is described.