This topic deserves a post of its own because it is perhaps the most dangerous thing that can happen on an aircraft. If you are aware of the risks, you can become an active participant in ensuring it never happens on your flight.A fire on a plane, much like on a ship, is nothing to take lightly. If it isn't brought under control quickly, it will spread rapidly through the structure. It’s not like being in a car where you can simply pull over and watch the fire from the side of the road...
Up there, there is nowhere to go. Aviation history teaches us that an uncontrolled fire can destroy a large aircraft in less than fifteen minutes.
In reality, the fire that causes the most fear is not an engine fire; engines are equipped with specific fire-suppression systems that are highly effective.
The real enemy is a fire inside the cabin. This could be caused by a short circuit (though these are usually easy to locate and isolate) or by a smoker who, in the middle of a nicotine craving, doesn't realize the immense danger they are putting everyone in. They lock themselves in the bathroom for a "quick puff," trying to "trick" the smoke detectors with their "infallible techniques" and then stealthily toss the butt into the bin without ensuring it is actually out.
It is true that lavatory waste bins have automatic fire extinguishers inside, but do we really need to let it get that far?
Another potential danger comes from prohibited or improperly packed items in the cargo hold. Fortunately, this is a problem that mostly affects cargo planes. Regardless, the holds of larger passenger aircraft are equipped with very effective fire detection and suppression systems.
Am I trying to scare you? No. As you can see for yourself, planes don't catch fire every day—not even every year! Furthermore, all flight crews are highly trained and regularly practice managing on-board fires in specialized simulators.
However, I want you to realize the actual risk involved so that you can play your part: pack your bags conscientiously, resist the urge to smoke, and report (report—don't start a fight!) any "strange" behavior or suspicious smells you might notice on board.
The crew will be grateful to you.
DontWorryFlyHappy!