One approach for computing plans for reactive agents is is to check goal statements over state trajectories modeling predicted behaviors of an agent. This paper describes a powerful extension of this approach to handle time, safety, and liveness goals that are specified by Metric Temporal Logic formulas. Our planning method is based on an incremental planning algorithm that generates a reactive plan by computing a sequence of partially satisfactory reactive plans converging towards a completely satisfactory one. Partial satisfaction means that an agent controlled by the plan accomplishes its goal only for some environment events. Complete satisfaction means that the agent accomplishes its goal whatever the environment event occur during the execution of the plan. As such, our plmmer can be stopped at any time to yield a useful plan.