Collecting the trajectories occurring in the city and mining the patterns implied in the trajectories can support the ITS (Intelligent Transportation System) applications and foster the development of smart cities. For improving the operations of inter-zonal buses in the cities, we define a new trip pattern, i.e., frequent bus passenger trip patterns for bus lines (FBPT4BL patterns in short). We utilize the passenger trajectories from bus smart card data and propose a two-phase approach to mine FBPT4BL patterns and then recommend inter-zonal bus lines. We conduct extensive experiments on the real data from the Beijing Public Transport Group. By comparing the experimental results with the actual operation of inter-zonal buses at the Beijing Public Transport Group, we verify the validity of our proposed method.