Aircraft empennage structures have impact resistance satisfying transport aircraft certification requirements (for example, FAR part 25 and/or other international certification requirements). The structures may be specifically embodied in leading edge structures that are preferably in the form of one-piece components formed from fiber-reinforced composite materials (e.g., reinforcement fibers such as glass fibers, aramid fibers and/or carbon fibers embedded in a polymeric matrix such as an epoxy resin). The leading edge structures will most preferably include an arcuate skin and longitudinally extending internal reinforcement which is generally Y-shaped and includes a planar rib element and a pair of planar divergent reinforcement arms. The rib element may be positioned so as to be coplanar with a longitudinal bisecting plane of the leading edge structure. A forward end of the rib element may thus be integrally attached aft of an apical end of the skin, whereas an aft end of the rib may be integrally attached to each of the reinforcement arms. According to certain embodiments, rigidity and thus impact resistance may be facilitated by providing the apical end of the skin with a greater cross-sectional thickness as compared to the attachment ends of the skin.