An apparatus operable to seal an opening in an aircraft fuel tank during a pressure test of the fuel tank is described. The apparatus includes a substantially dome shaped body having a perimeter. The body further includes a rim extending in an orthogonal direction about the perimeter and a flange extending in a normal direction from the rim and about the perimeter. The flange is sized to engage the fuel tank about the opening. The apparatus further includes a sealing gasket proximate an intersection of the rim and the flange, extending completely around the perimeter. The seal is oriented to provide a sealing function between the fuel tank and the body as pressure is increased within the fuel tank.