You are making things up. There are no licensing requirements to operate a homemade jet engine, and building a small-scale jet engine for science experiments, although difficult and potentially dangerous, is not against any law in the United States and has been done by many creators on YouTube. 

Show me the relevant laws and regulations specifically against operating a home jet engine if I'm wrong.
spam lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor creativity violence