Energy-efficient and time-efficient reconfiguration strategies for formation flying of autonomous agents are presented. It is assumed that a finite set of possible formations is given, and that the probability of each formation in this set is known a priori. The idea is to move the agents to floating stations in the idle time, i.e. the time between the accomplishment of the last reconfiguration task and the issuance of the next reconfiguration command, to minimize the expected value of the energy consumption or reconfiguration time. In the energy-efficient strategy, the position of each floating station is derived as a function of the agent's current position, and the weighted center of gravity of the set of possible positions for that agent. In the time-efficient strategy, on the other hand, it turns out that the problem of finding the position of the corresponding floating stations is non-convex. To address this issue, a method is provided to reduce the global minimum search space to a convex compact set. Consequently, a numerical procedure for finding an arbitrarily precise global minimum is proposed in this case. The effectiveness of the proposed strategies is illustrated via simulation.