Results of an experimental programme aimed at evaluation of fatigue crack growth (FCG) rates in an aircraft Al 2124 alloy in T851 treatment conditions are presented and discussed. Measurement was performed in both regions of stable crack growth and threshold region. FCG rates were measured in both L-T and T-S directions to evaluate sensitivity of FCG resistance on different microstructure orientation. Different load asymmetry conditions R = Fmin / Fmax were used, namely R = 0.1 and 0.6. Repeated measurements in more than one specimen at each condition enabled to evaluate reproducibility, scatter of measurement and to perform regression analyses including confidence bands and tolerance limits. The reproducibility of measurement was particularly good for L-T orientation. In this case, threshold values were somewhat higher and FCG rates lower in comparison with the T-S orientation. The results are completed with probabilistic assessment of residual life in specific types of components. Examples of effects of scatter on residual life are shown and discussed.