For many aviation safety studies, aircraft behavior is represented using encounter models, which are statistical models of how aircraft behave during close encounters. They are used to provide a realistic representation of the range of encounter flight dynamics where an aircraft collision avoidance system would be likely to alert. Since 2019, software related to these models have been released under permissive open source licenses to promote community development and enable commercialization. Version 1.4 brings a variety of performance improvements and introduces the correlated terminal encounter models based on terminal area radar or OpenSky Network processed tracks. Software to sample the terminal model is scheduled for an upcoming release.