One of the important features of airport passenger terminal layout is passenger orientation (wayfinding). Many people have difficulty in locating their desired destination within an airport despite the availability of information signs. This paper describes the use of a quantitative measure, or visibility index, to evaluate the ease of orientation in the departure lounge of Hong Kong International Airport. Based on the visibility index, a new set of level-of-service standards for orientation is proposed. The findings of this paper are compared with those of previous studies.