The fractional Brownian motion (fBm) was verified as a model to describe the complex behaviour of a commercial airlift reactor. A pressure signal recorded was analysed and predictions were made with the fBm model. It can be concluded that the pressure signal airlift reactor exhibits the features of the fractional Gaussian noise and not of the fBm. Modelling of the pressure signal with the fractional Gaussian noise (fGn) can be used for control purposes or fault diagnosis. The characteristics of the commercial airlift reactor are encountered in various reactors which shows the great potential of the fGn to describe pressure signals in such reactors. As the variations of the pressure signal can be described by the fGn, the fBm is still a potential candidate to describe variations over the longitude of the reactor.