An air separator in a gas turbine engine includes a cylindrical member and a seal flange having a flange body extending radially outward at a rearward end of the cylindrical member. A head portion is located at a radially outer free end of the flange body and includes an axial flange located axially rearward of the flange body and defining a rearward seal face for engagement with a blade disc forward face, and a forward cantilevered head mass extending axially forward from the flange body. An axial dimension of the head mass, from a connection with the forward side of flange body to an axially forward face of the head mass, is greater than a maximum radial dimension of the head mass, from a radially inner side of the head mass to a radially outermost side of the head mass.