Deep Neural Network (DNN)-based vision systems could improve passenger transportation safety by automating processes such as verifying the correct positioning of luggage, seat occupancy, etc. Abundant and well-distributed data are essential to make DNNs learn appropriate pattern recognition features and have enough generalization ability. The use of synthetic data can reduce the effort of generating varied and annotated data. However, synthetic data usually present a domain gap with real-world samples, that can be reduced with domain adaptation techniques. This paper proposes a methodology to build simulated environments to generate balanced and varied synthetic data and avoid including redundant samples to train classification DNNs for passenger seat analysis. We show a practical implementation for detecting whether luggage is correctly placed or not in an aircraft cabin. Experimental results show the contribution of the synthetic samples and the importance of correctly discarding redundant data.