The primary objective of this paper is to develop an algorithm for integrating a user’s kinematic position solution based on corrections provided by the EGNOS, UK SBAS, and AL-SBAS systems. To date, aviation research in Poland has primarily employed a single EGNOS augmentation system. In contrast, this study is the first to use three independent SBAS augmentation systems within a single experiment, which constitutes a novelty in this research area. This approach is crucial for ensuring redundancy in position determination and for controlling the calculations of the determined coordinates. To this end, a weighted mean model was applied to determine the user’s coordinates. Measurement weights were defined as functions of the inverse number of tracked satellites and the inverse of the point position error ellipsoid. Using the proposed computational strategy, the user position was determined in ellipsoidal coordinates (BLh), and the precision of the solution was additionally assessed by calculating the standard deviation and the mean error of the arithmetic mean. The computational strategy was validated through an airborne experiment using a VTOL WingtraOne UAV equipped with a NovAtel OEM7500 GNSS receiver. The results indicate that the mean value of the standard deviation of the determined position does not exceed 3.01 m when measurement weights are defined as the inverse of the number of tracked satellites, and 2.60 m when weights are defined as the inverse of the point position error ellipsoid. Weighting observations using the inverse of the point position error ellipsoid produced better results, as it is calculated based on the actual mean measurement errors. The proposed research methodology can be applied to other SBAS augmentation systems within areas of overlapping correction coverage. In particular, the developed methodology can be applied to SBAS APV approach-to-landing operations in air navigation.