Air data sensing apparatus comprising: an aircraft panel; a blister arranged on a surface of the aircraft panel, the blister comprising an upstream portion and a downstream portion, the upstream portion being rounded in three dimensions and having a rounded outer edge surface spaced laterally from the aircraft panel; a plurality of apertures in the surface of the aircraft panel, the apertures being adjacent to the upstream portion of the blister, and spaced from the blister; a plurality of conduits, each conduit being in fluid communication with a respective aperture; and one or more pressure sensors arranged to measure a pressure in each of the conduits.