Based on the premise that sharp leading edges are beneficial for launch, ascent and landing phases several concepts for sharp leading edges of winged re-entry vehicles have been scrutinized. On the other side blunt leading edges mitigate the heat loads during re-entry. Therefore, to comply with material temperature limits either sharp leading edges have to be cooled or the curvature shape must be changed between ascent/landing and re-entry flight phases. Sharp leading edge shapes are enabled by transpiration cooling, heat pipe or other heat load relieving concepts. Changing the wing profile, i.e. shape morphing is a research topic in aircraft development which progresses steadily. Basic feasibility of concepts for morphing the leading edges of hypersonic flight vehicles has been studied within a recent ESA technology contract. A shape morphing compliant mechanism leading edge fully based on CMC materials indicates advantages compared to other concepts.