The objective of this paper is to model, simulate and analyze platooning (separation) control for a fleet of 6 quadcopter units. Control for 6 degrees of freedom (x, y, z, φ, θ, ψ] is modeled for each individual quadcopter using a cascaded linear feedback control system, with the fleet modeled as leader-follower. The primary motivation of this research is to examine string instability arising from the 'accordion effect a phenomenon observed in leader-follower systems due to which positioning or relative spacing errors arise in follower vehicles due to sudden changes in lead vehicle velocity. First, a PID separation controller is designed for a nominal case, where communication within the system is ad-hoc. Steady state separation/positioning errors for each member of the fleet are observed and documented. Second, lead vehicle acceleration is then provided to each controller (as a feed forward term), which is used to compare controller bandwidth requirements to ensure relative string stability, within acceptable error bounds. Thus the key contribution of this work is a separation controller for a fleet of quadcopters, with quantitative analysis of the string stability, using simulation data from MATLAB Simulink.