In the process of synthesising a satellite communications plan, a large number of possible configurations has to be analysed in a short amount of time. An important part of the process concerns the allocation of channels and polarisations to the various systems. It is, of course, desirable to make these allocations based on the aggregate carrier/interference ratios, but this needs a considerable amount of time, and for this reason the single-entry carrier/interference criterion is usually employed. The paper presents an integer programming model based on an approximate evaluation of the aggregate carrier/interference ratios, which is fast enough to justify its application in the synthesis process. It was developed to help the elaboration of a downlink plan for the broadcasting satellite service (BSS) of North, Central and South America. The official software package of the 1983 Administrative Radio Conference (RARC 83), responsible for the planning of the BSS in region 2, contains a routine based on this model.