Due to instability and specific configuration of tailless aircraft, there should be a controller with capability of stabilizing the aircraft in various maneuvers and flight conditions and also to have desired robustness against different parametric and non-parametric uncertainties. Different researches are done in the field of controlling such aircraft. But, most of them are concerned with longitudinal motion of the aircraft and its modes or stable maneuvers. In this paper, we design a multi input-multi output combined model-reference adaptive controller for a tailless aircraft. Coordinated turn is an unstable maneuver, itself. The addition of the instability of this maneuver and the instability of a tailless aircraft causes a highly unstable situation. Combined model-reference adaptive control benefits the aggregation of the tracking error and prediction error. Combining these two sources of errors alleviates the transient response characteristics, and a combined model-reference adaptive controller has better performance comparing to the classical model-reference adaptive controllers (with tracking error as the only source of parameter estimation error), and this property could be useful in highly unstable systems like tailless aircraft. Here, after extracting the equations of motion of an aircraft and exerting the conditions of coordinated turn maneuver, we design a combined model-reference adaptive controller for a tailless aircraft. The simulation results show accuracy of the designed controller in stabilizing the aircraft during the coordinated turn maneuver and its robustness against uncertainties.