This was always an issue for me. One flight I was on, a particularly turbulent flight at night where we could see lightning at times, I suddenly smelled some kind of burning, smoke smell. I started panicking, convinced we had been struck by lightning and were on fire. Two flight attendants were chatting nearby and I asked about it and they said the smell was from the oven. I was like, oh okay. But then I remembered they only served cold sandwiches and I was like, oh my god we are on fire and they're trying to keep me calm by telling lies! Look how they are chatting about TV shows, probably the other flight attendants are in the back freaking out and they are the decoy to keep us calm! Needless to say, we were not on fire, we did not crash, we landed safely and it's not likely the flight attendants were discussing TV shows and laughing while a fire was being put out somewhere. Probably there was an oven that was being cleaned or used for a special meal or maybe it was for coffee, who knows, but there are a lot of weird smells just as there would be on a bus or even in your car. Learning to focus on reality (like the fact that the flight attendants are just standing there chatting and there is no big conspiracy) can help you stop those thoughts.