Weapons development is moving towards longer ranges, especially regarding missile weapons. The missile systems that warships can carry nowadays have a range that is greater than the range of the ship's own sensors. To fully utilize the range of the missile system, external sensor functionality must therefore be used. This work aims to evaluate the combat effectiveness of surface combatants' air defence with and without the support of a naval UAV equipped with AESA radar. In the future, combat capability against surface combatants will be studied with the same external sensor functionality. To evaluate combat effectiveness, the simulation tool Ship Air Defence Model is used. A naval UAV equipped with AESA radar enables reconnaissance at longer distances compared to reconnaissance with mast-mounted radar. For the increased radar horizon to be useful, however, the carried sensor must be powerful enough to detect radar echoes generated by potential threats. A reasonably sized naval UAV for use from a corvettesized surface combatant has limitations regarding the size and weight of the on-board sensors. Results based on the given scenario show that the combat effectiveness of an air defence system supported by a naval UAV is limited by the radar's power rather than by the radar horizon. They also highlight the importance of sizing the air defence sensor systems according to the range of the weapons so that the latter can be fully utilized.