A fan for gas turbine engine that includes hub and annular array of fan blades mounted to hub and extending radially outwardly from hub, each fan blade includes blade root. The hub includes a plurality of hub grooves having shape complimentary to shape of blade root and each hub groove receives and radially retains one blade root. A slot is provided on the suction side and on the pressure side of each blade root. Plurality of keys is provided, each key engages with slots in one blade root and with corresponding hub groove so as to axially retain fan blade. The key includes two arms and joining member, two arms are received in slots provided on blade root and joining member extends between the arms. Interface is defined between key arms and slots in blade root, and greater or equal percentage of interface is curved than is planar.