The software's speech recognition algorithm transforms a spoken voice signal into a sequence of words. The speech understanding algorithm then converts the individual words into semantic units. These may be callsigns, command types or command values. The system also uses command prediction to improve speech recognition and understanding. The command prediction system uses radar, flight plan and weather data to automatically identify the callsigns of aircraft in the vicinity that could soon be addressed. It also provides potential command types and corresponding values for each callsign. Command types include changes in direction, speed or altitude. For this purpose, the command prediction system uses radar, flight plan and weather data. The results of the speech understanding process are automatically displayed on the controller's radar screen.