In this paper, the gyro-travelling-wave tube ( gyro-TWT ) is proposed to be used as the transmitting tube in airborne early-warning radars ( AEWRs ). Since the gyro-TWT is one of the members of the recently developed gyrotron family that comprises the most powerfull sources of millimeter waves, the radars employing the gyro-TWT will have many significant advantages when compared with the conventional AEWRs. In order to get further insight into the operation and performance of gyro-TWT, the results of a large-signal nonlinear analysis of this device are presented and the effects of the different operating conditions on the performance are investigated.