Abstract: An insulation device for an aircraft, comprising a blanket comprising a layer of insulation filling enclosed in a cover and having provision areas for the passage of aircraft components, these areas being devoid of insulation filling and being formed by a surface junction of two opposite faces of the cover inducing a recess in at least one face. The insulation device comprises an associated detachable complementary assembly to cover at least one of the provision areas, the assembly comprising a portion of insulation filling shaped to fit into the corresponding recess, and a retention arrangement for retaining this portion of filling. The retention arrangement is provided with a detachable arrangement for fixing the detachable complementary assembly on at least one face of the cover.