SIPE-2 is a partial-order AI planning system that supports planning at multiple levels of abstraction. It has the properties required by our agent model, including the ability to generate action sequences that include parallel actions, conditional actions, and resource assignments, and the ability to perform temporal reasoning. SIPE-2 can also be used to modify previously generated plans, an essential capability for run-time replanning. In contrast to most AI planning research, heuristic adequacy has been one of the primary goals in the design of SIPE-2. Example applications include planning the actions of a mobile robot, planning the movement of aircraft on a carrier deck, travel planning, construction tasks, the problem of producing products from raw materials on process lines under production and resource constraints, and joint military operations planning .