Frangible fasteners with flexible connectors for unmanned aircraft, and associated systems and methods are disclosed. A representative aircraft includes a fuselage portion, a wing portion, a winglet carried by the wing portion, and a frangible fastener coupling the winglet portion to the wing portion. The frangible fastener can include an outer body with a first portion in contact with the wing portion, a second portion in contact with the winglet portion, and a frangible portion between the first and second portions. A flexible member is positioned at least partially within the outer body and is connected to the first portion so as to extend through and out of the second portion. A stop element is carried by the flexible member.