The economic requirement for reductions in horizontal separation standards on high density oceanic routes such as the North Atlantic has motivated the search for a navigation and guidance system combining compatibility with foreseeable separation criteria while at the same time remaining cost effective. In this paper, by the Executive Vice-Chairman of the International Air Navigators' Council, an attempt is made from that point of view, to suggest various systems which are envisaged as meeting the most stringent requirements foreseen. Consideration is given to accuracy requirements, avionic hardware, and optimization of crew responsibilities based on airline experience derived over the past decade. Mr. Waldman is a navigator with Air Canada, but the views expressed are not necessarily those of the Air Canada Management.

1. Introduction. In the spring of 1965, an I.C.A.O. Special North Atlantic Regional Air Navigation Meeting (NAT/ RAN) approved by a margin often to two a reduction in nominal lateral separation from 120 n.m. to 90 n.m. in the ‘principal area’. (The ‘principal area’ of the NAT Region is the area delineated by Gander Oceanic, Lisboa Oceanic, New York Oceanic, Reykjavik, Shanwick Oceanic, and Sondrestrom, South of 700 North.)