A system and method for controlling a vehicle system control movement of the vehicle system along a route. The vehicle system includes one or more propulsion-generating vehicles. A propulsion-generating helper vehicle is temporarily added to the vehicle system such that the helper vehicle increases one or more of an amount of tractive force or an amount of braking effort generated by the vehicle system. The helper vehicle may be added during movement of the vehicle system. The system and method may add the helper vehicle without de-linking the propulsion-generating vehicles in the vehicle system from each other. The system and method optionally may control movement of the propulsion-generating vehicles and the helper vehicle according to a trip plan that designates operational settings as a function of at least one of time or distance along the route.