During the last years, the International Symposia on Precision Approach and Automatic Landing (ISPA) have shown a considerable change in the significance of integrated landing systems. At the first ISPA conference in 1995, the combination of inertial sensors and GNSS receivers was thoroughly discussed and appeared to be a very promising concept, especially with respect to ‘Integrity’ and ‘Continuity’. Ever since, this particular combination of sensors has received little attention. A comprehensive discussion of the technical background of this setback for integrated landing systems did not take place, primarily because of the popular opinion that the Kalman filter algorithm, which is the system integration kernel, is not sufficiently stable. The true reason has meanwhile been identified. The aiding of an inertial navigation system by only one GNSS antenna is insufficient in phases of low aircraft dynamics such as in the case of final approach. Instead, a multi-antenna system is required with antennas widely distributed over the aircraft structure. This latter approach, however, causes problems due to structural flexibilities. To show that an integrated system based on inertial sensors and widely distributed GNSS antennas is technically feasible, the paper discusses the following topics. (1) Unstable system performance during final approach for 1-antenna-aiding. (2) Improving the system performance prior to using additional antennas. (3) Effect of the antenna distribution. (4) Integrated systems for distributed sensors and flexible aircraft structures. The paper shows that integrated systems are still an attractive candidate for automatic landing equipment preserving the advantages with respect to ‘Integrity’ and ‘Continuity’.