No experience with "park fliers" but the electric models that I have flown for others at the field have an on-off switch controlled by the transmitter.

If a Pk. Flier has same, then shut the motor off, and the model is NO LONGER "powered". So catch it if you can. Same for RC glider.

Same for a gliding/DTing FF, yet there might be some contention with a free-wheeling prop on a rubber-powered model, yet that is actually a brake and not power, while a "folder" is definitely not powered.

Never overlook the options.