This paper introduces a system for transmitting the aircraft guidance command over a narrow band communication channel in a secured way. The paper takes into account the noise, which exists in the guidance center. The proposed system is based on speech recognition and consists of two modules; one on the ground and the other is on the onboard. Guidance command words are modeled using Hidden Markov Modeling (HMM) and stored in the onboard module. During operation the input guidance word is processed and transmitted in a coded form from the ground module to the aircraft. The onboard module recognizes the words using HMM speech recognizer. The feature extraction technique used in this work is the Perceptual Linear Predictive (PLP) coding, which shows good immunity to noise. The performance measure is the recognition accuracy at different SNRs, as well as the achieved compression ratio of the transmitted message.