In this paper, optimal guidance laws for multiple vehicles formation flight are addressed. The proposed laws are obtained as state-feedback solutions of linear quadratic optimal control problems to minimize the time varying energy cost with terminal constraints on position and velocity. Since the proposed laws are able to control the flight time, they are possible to make all vehicles join the formation concurrently at a specified time. A method to compensate the acceleration or maneuver of the formation leader is included in the guidance laws. And an inter-vehicle collision avoidance scheme is also considered. The performance of the guidance laws is tested via various numerical simulations.