A method and system is disclosed for using inertial sensors in an Inertial Navigation System (INS) to obtain analytic estimates of angle-of-attack (.sub..alpha.) and sideslip angle (.sub..alpha.). The inertial sensors consist of one or more accelerometers which produce the estimated signals for angle-of-attack (.sub..alpha.) and sideslip angle (.sub..beta.). Three methods are shown for obtaining .sub..alpha. and .sub..beta. estimates from INS information and are programmed into a nonlinear simulation of a relaxed stability aircraft requiring a high level of artificial stability augmentation in its flight control system. Simulation results from the nonlinear simulation for each of the three methods were compared with the results obtained when conventional probes were used to obtain direct measurements of .sub..alpha. and .sub..beta.. Based on these comparisons, a method for determining .sub..alpha. and .sub..beta. analytically which estimates the turbulence level in each axis is combined with one of the three methods to provide derived inertial values for providing control system feedback to an aircraft.