In this paper, an active fault-tolerant flight control system against sensor/actuator failures for unmanned aerial vehicles (UAVs) is proposed. First, an approach to detecting and isolating UAV sensor failures affecting the mean of the Kalman filter (KF) innovation sequence is proposed. Second, an adaptive two-stage linear Kalman filtering algorithm is used to isolate the sensor and actuator faults and to estimate the loss of control effectiveness and the magnitude of degree of stuck faults in a UAV model. Control effectiveness factors and stuck magnitudes are used to quantify the faults entering the UAV flight control system through actuators. In the case of a sensor fault, the faulty sensor is isolated, and the KF that ignores the feedback from the faulty sensor is built. If the fault is an actuator fault, then the actuator fault isolation and identification are performed using the adaptive two-stage KF. The parameters of the feedback controller are tuned by the control reconfiguration procedure. In the simulations, the longitudinal and lateral dynamics of the UAV model is considered, and the detection and isolation of sensor failures are examined. Some simulation results for the actuator fault isolation and identification are given. Partial loss and stuck faults in actuators are considered. A design of reconfigurable flight control against sensor/actuator failures is implemented.