Flight-simulation tests were carried out on sheet specimens notched "by an open hole (Kt = 2.66). The material was 2024-T3 in three conditions; Alclad, bare and chemically milled. The crack initiation period and the crack propagation period were considerably shorter for the Alclad material. The significance of the cladding, both for constant-amplitude loading and variable-amplitude loading, is analysed. Information from the literature is summarized. Practical aspects for aircraft application are indicated.