Radio beacons, at around 115 MHz (VHF, VOR), are used as opportunity donors in a passive radar configuration. Full-wave simulation of three categories (according to size) of aircrafts shows that their bistatic RCS are statistically comparable without any additional information but perform differently in time (while flying). This discrepancy can be exploited to recognize the aircrafts among the categories. Measurements confirm these ideas and indicate that it may be possible to differentiate the aircrafts among the same category. Encouraging initial results were obtained using Convolutional Neural Networks to classify airplane categories combining simulated bistatic RCS results and real trajectories (collected from ADS-B data).