In this paper, the concept of two-stage energy-optimal reconfiguration strategy for formation flying of autonomous agents is presented. It is desired to move the agents to a special designated formation in the idle time (the time between the completion of the current formation mission and the issuance of the next reconfiguration command), in order to minimize the expected value of the reconfiguration energy consumption. The position of each agent in the special designated formation is obtained as a function of the agent's current position and the weighted center of gravity of the set of possible positions for that agent. It is shown that this strategy can reduce energy consumption considerably compared to conventional strategies. In the case of constrained acceleration, it is shown that the results remain the same as the unconstrained case if the reconfiguration time is sufficiently longer than its minimum possible value. The effectiveness of the proposed strategy is illustrated by simulation. (C) 2012 Elsevier Ltd. All rights reserved.