The second prototype of the JF-17 Thunder’s twin-seat variant—the JF-17B—is currently undergoing flight tests in China. A total of three JF-17B prototypes are in production after requests by potential third-party customers for a twin-seat variant that could be used for training and evaluation purposes. Two prototypes will go to the Pakistan Air Force (PAF). In addition to a tandem seat, the JF-17B incorporates several design changes to its single-seat counterpart, including a modified vertical stabilizer, dorsal spine (potentially for fuel to compensate for the space lost from the additional seat), enlarged nose and three-axis fly-by-wire (FBW) flight control system.