In this paper, the reliability of tunable ferroelectric thin film capacitors has been addressed. The long term stability of tunable capacitors based on Ba0.3Sr0.7TiO3 films deposited by chemical solution deposition onto an alumina substrate was investigated by monitoring their tunable performance as a function of the number of ON-OFF switching cycles and as a function of time. The conditions of civil aeronautic applications were chosen to plan the lifetime experiments. More than 300×106 of switching cycles with an amplitude of 150 V and frequency of 1 kHz were successfully applied to the investigated capacitors without damaging them. Moreover, no degradation in the C-V characteristic was observed after the application of 150 V dc voltage during 15 h. Additionally, the effect of illumination of the ferroelectric film by ultraviolet light on the tunable performance of the capacitors has been investigated. A positive effect of such illumination on the C-V characteristics of ferroelectric capacitor has been found.