 In addition, the size of the empennage was redesigned so that the vertical stabilizer had nearly twice the area of that of the standard B-57B.Its height was increased to and the width increased, improving longitudinal and asymmetric control for greater stability at very high altitudes (up to ).Another obvious change was the replacement of the Wright J65 turbojets with Pratt & Whitney TF33-P-11 turbofan engines.