Today's enviornmetnal problems cannot be solved solely with technical and economic measures, a better understanding of human attitudes and behaviors is also required. This study examines air travelers' environmetnal knowledge, environmental attitudes, environmental behaviors, and pro-environmental air travel behavior in Taiwan. The relationships between environmental consciousness components with the socio-demographic variables are also tested. A field survey was administered to collect data from airline customers. The results show that Taiwanese passengers have moderate to high levels of environmetnal knowledge and overall possess a favorable environmetnal attitude. While they engage in general environmentally friendly behavior quite often, their pro-enivornmental air travel behavior is low. In addition, some differences concerning environmetnal knowledge, attitudes and behaviors exist across gender, age, and education factors. The contribution of this research is to broaden the udnerstanding of airline customers by examining their environmental consciousness and provide insights for airlines' selective marketing to enviornmentally concerned customers.