In the 1960s, as a result of the reduction in pressure-sensing accuracy of barometric altimeters with increasing altitude and as a function of the operational ceiling of the aircraft at that time, an increased VSM of 600 m (2000ft) was established for use between aircraft operating above FL290, established as a changeover level.

In the mid-1970s, the series of world fuel shortages and the resultant rapid escalation of fuel costs, allied to the growing demand for a more efficient utilization of the available airspace, emphasized the necessity for a detailed appraisal of the proposal to reduce the VSM above FL 290.

In 1982, coordinated by the ICAO Review of the General Concept of Separation Panel (RGCSP), some countries initiated programmes to study comprehensively the question of reducing the VSM above FL 290.

In December 1988 the results were considered by the RGCSP at its sixth meeting (RGCSP/6). After exhaustive studies employing quantitative methods of risk assessment to support operational decisions concerning the feasibility of reducing the VSM, the level of risk that is deemed acceptable was termed the Target Level of Safety (TLS) which is expressed in terms of 2.5 x 10^-9 fatal accidents per aircraft flight hour as a consequence of technical (altimetry) errors.

At the seventh meeting of the RGCSP (November, 1990), the Panel completed the global guidance material for the implementation of the 1000 ft reduced vertical separation minimum (RVSM). The main purpose of the material (Doc. 9574) was to provide regional planning groups (RPG) with the criteria, requirements and methodology for the development of documents, procedures and programs to enable the introduction of the RVSM within their particular region.