This article quantifies the importance of the future desired trajectory in determining the exact-output-tracking input for nonlinear, nonminimumphase systems by using system inversion techniques. It is intuitive that the effect of the desired output's distant-future values, on the output-tracking input at the current time instant, should be small. Therefore, at a current time instant (t(c)), preview information of the desired output in a finite-time window [t(c), t(c) + T-p] should be sufficient to compute the output-tracking input with an arbitrarily small prescribed error, if the preview time T-P is sufficiently large. The contribution of this article is the quantification of the needed preview time T-p by using the benchmark VTOL aircraft model as an example. Additionally, simulation results are presented to evaluate the efficacy of the finite-preview-based stable-inversion approach. (c) 2006 Elsevier Ltd. All rights reserved.