These models are a development of the simple balsa glider (although this ancestry is sometimes difficult to recognize!) married to model rocket propulsion. They are launched vertically on A to G motors (single or two stage propulsion allowed), and are then glide recovered. A "Boost Glider" is the version in which the rocket motor is ejected at the end of its burn, while in a "Rocket Glider" the motor casing stays with the vehicle during its glide recovery. "Parasitic" gliders, which go aloft carried on a separate rocket launch vehicle, from which the glider detaches to glide return on its own (while the launch rocket must have its own recovery system - tumble, streamer, parachute), may also be entered. The flights are timed from first motion on the launch pad to the moment of landing, or the model is lost to sight. Each entrant can launch up to 3 flights - of the same model or different ones, and their best individual flight time will count in the scoring. The winner will be the entrant with the longest flight time over all the flights entered.