Vibration Correlation Technique (VCT), a non-destructive method for axial buckling load determination, has shown major advantages for a range of industrial applications. VCT allows to correlate the ultimate load or instability point with rapid decrement of self-frequency response. Nevertheless this technique is still under development for thin-walled shells in particular. In this paper, the authors discuss experimentally verified methods to extend vibration correlation approach in order to predict an actual ultimate load level of unstiffened cylindrical shells loaded in axial compression. Validation study includes manufactured carbon fibre cylinders that were laser-scanned during repeated loading up to the instability point.