I've thought about this myself, and wonder if it would be possible to mount small fans in the engine with tappered pieces of tissue paper and some LED's.
Could maybe work in other than vertical flights.
Just a suggestion. Some of those larger ones with different colors (red - yellow) can look pretty realistic.
When I was involved in doing recruiting demonstrations for the Boy Scouts, I would go to schools. Set up a "campsite"- a tent, folding camp table, cooking tripod, and a wood fire. The fire would be some logs arranged log cabin style with one of those store bought fire things you see around Halloween.
I'd light some pine incence and have the lights dimmed when the kids walked in. They'd Ohh and Ahh, seeing their auditorium or gym transformed into an outdoor scene.