<p>This study investigates the impact of tightening torque and assembly parameters on the sealing performance of aircraft flared tube fittings. An integrated approach is used, combining finite element analysis (FEA) with experimental validation. Based on contact theory, a finite element model was established to analyze contact stress distribution. This analysis revealed a proportional relationship between the real contact area and the average contact stress. This finding enabled the application of percolation theory to identify the critical contact pressure necessary for effective sealing. A full assembly model was then developed to assess the impact of tightening torque and misalignment on sealing performance. Experimental tests were performed on standard aircraft tube fittings (nominal diameter <i>d</i>₀ = 6 mm) and showed strong agreement with simulations. The measured minimum tightening torque of 20.7 N·m deviated by only 7.6 % from the simulated value of 22.28 N·m. Both methods consistently identified axial misalignment as the dominant factor influencing sealing performance. The proposed methodology provides a reliable framework for predicting sealing performance. It can be extended to other types of flared fittings by adapting the parameters.</p>