Apparently that is what happened on a recent El Al flight from Tel Aviv to Bangkok when a passenger set the toilet waste bin ablaze, according to The Times of Israel.
The passenger, needing a nicotine fix went to the restroom and had a smoke - apparently the cigarette smoke wasn’t enough to set off the smoke detectors inside the toilet’s space. To hide the evidence, he tossed the cigarette butt into the trash receptacle (full of paper) and the paper combusted. This time the alarm was heard and flight crew came to the rescue with extinguishers. If you’re reading this, you’re already asking why didn’t the smoker run water of the cigarette butt or perhaps, who the hell smokes in airplanes in the year 2022.
El Al about their airplane

El Al said in a statement, “The flight continued as scheduled and landed safely at Bangkok Airport,” they then added the individual would face legal action in Israel. Interestingly, the flight crew did not inform the local police in Thailand upon arrival, as “no damage was caused to the plane.”
Perhaps had El Al called in the police in Bangkok this tale would be one where folks read and say, yes, that’s a bad idea, let’s not do that.” Instead, El Al appears to be sending the message, “you can set the lavatory trashcan on fire and continue on your merry way.
Please don’t set the airplane toilet on fire. Thank you