The work presented concerns the development of a quantum-based decision making model utilised in the identification of optimal strategies in engineering design under uncertainty in a quantum-like entangled decision making, assessing intention interference. Several experiments and decision making paradoxes have manifested the deficiency of rationality assumption employed by classical decision making theory, with humans often violating the hypotheses of the expected utility theory and Game Theory by making irrational choices. Quantum Decision Theory (QDT) is the basis of the proposed decision making model, since only this theory can be employed to develop an operational tool in any social interplay, given the preferences of the individuals/players, to assess the quantum probabilities of their strategies. The decision makers' brain is assumed of a dual nature, with brain processes divided to conscious and subconscious constituent parts and the computed quantum strategic probabilities consisted of two parts, the first one being rationality related and the other one capturing biases, emotions and feelings. Hence, given a priori the preferences of the decision makers, this model can be utilised as an operational tool for decision making under uncertainty in the presence of entanglement assessing the quantum probabilities of the players' strategies in any engineering design. This quantum-based decision making model, identifying the optimal strategic choices of the stakeholders involved, is employed in the presented conceptual design of an Unmanned Air System (UAS), based on both the stakeholders' rationality, personal intuitive feelings and behavioural biases.