This thread has just reminded me of an incident many years ago, where the pilot made the request, “ is there a mechanic onboard?”
This was in early 80’s on a charter airline called Pyramid airlines who were operating really old DC 3’s to shuttle workers between Cairo and oilfields in the Western desert. They were actually using dried up lake bed as a landing strip.
In this case the pilot wasn’t looking for the services of a mechanic, but rather access to a tool box. He couldn’t start one of the engines and needed to remove the engine cowling. As I recall, I think the engine was finally started by throwing a cup of jet fuel into the air intake???
I had one or two other scary moments flying with them that would make your hair curl!