A vane arc segment includes an airfoil fairing that has first and second platforms and an airfoil section. The platforms have first and second openings that open into the airfoil section. The platforms each define first and second circumferential mate faces, forward and aft sides, a gaspath side, a non-gaspath side. The first platform has a first flange that projects radially from the non-gaspath side aft of the first opening and a second flange that projects radially from the non-gaspath side forward of the first opening. The first and second flanges are exclusive flanges on the first platform. The second platform has a third flange that projects radially from the non-gaspath side aft of the second opening.