Sophisticated general purpose mathematical programming systems are available from numerous sources, both academic and commercial. This paper documents the application of one of the most widely used commercial systems, IBM`s Mathematical Programming System-Extended(MPSX). A general MPSX-multistage algorithm is developed and applfied to the solution and simulated usage of a linear programming aggregate operations planning model. Deterministic applications of a multiperiod linear programming aggregate operations model are simulated in exploring the sensitivity of solutions to changes in both the horizon length and ending conditions. The results of these several different deterministic applications are briefly discussed in the paper.