Abstract: A gas turbine engine fan blade containment assembly (38) comprising a generally cylindrical, or frustoconical, metal casing (40) has an upstream portion (56), a blade containment portion (54) and a transition portion (58). The upstream portion (56) has a flange (52) connecting the metal containment casing (40) to an axially adjacent casing. The upstream portion (56) of the casing (40) has a greater diameter (D1) than the diameter (D2) of the blade containment portion (54) and the blade containment portion (54) has a greater thickness (T2) than the thickness (T1) of the upstream portion (54). The transition portion (58) connects the blade containment portion (54) and the upstream portion (56) to transmit loads from the blade containment portion (54) to the upstream flange (42).