Borides of early transition metals are considered very promising materials for several applications, the most appealing one being currently in the aerospace. The present contribution deals with two UHTC ZrB2-based materials reinforced, respectively, with SiC in form of chopped fibre or fine particulate. Addition of SiC fibre enabled to double fracture toughness. Suitability of this system for the sharp leading edge technology was tested in an arc-jet supersonic plasma wind tunnel using very sharp technological demonstrators (0.1 mm radius of curvature). Net heat flux up to 7 MW/m\ though induced equilibrium surface temperature at the tip up to 2450 °C, did not give rise to partial rupture or failure of the specimens. Both UHTC wedges survived severe aero-heating by re-distributing heat over colder regions downstream of the sharp tip. Copyright © (2012) by the International Astronautical Federation.