What's making it fly?

https://www.tiktok.com/@kaosurvive/video/7123228044000513307

I see a flame in the back, what is it using and how long can it fly?

https://www.tiktok.com/@kaosurvive/video/7124497790285139226

The other like helicopter and airplanes with propellers are obvious. But the model jet, what is giving it thrust?

https://www.tiktok.com/@kaosurvive

I assume those models are very $$$$$!