IAA airport firefighter.
Halon is most certainly used on aircraft - it is the extinguishing agent that all others are compared to. Halon (1211 and 1301 specifically) are ideal for aircraft fire extingushing systems. They leave no residue (no clean-up), they are essentially non-toxic, it takes a very small quantity of agent to extinguish the fire, and they can be stored for long periods of time prior to use. The newer halon replacements, such as Halotron I, Inergen, and FM200 work, but not as well as 1211 and 1301 did.
A photoof the two engine halon extinguishing agent tanks on a 737. They live in the left main wheel well, both are about the size of volleyballs (scroll down on the page, 3rd photo down).
ABC dry chemical*, on the other hand, is nasty stuff when around aluminum. The ammonium phosphate base that the dry chemical is made out of is murderously corrosive on aluminum. Once discharged, the powder can travel quite a long distance and settle on objects remote from where the extinguisher was used, causing corrosion problems that you didn’t expect or anticipate. On an airport ramp, or inside the world’s largest indoor space (Boeing), ABC dry chemical is a huge liability. For that reason, ABC dry chemical fire extinguishers are not allowed on airport ramps/aprons or in airport fuel facilities in the US.
Back to the OP…
The best system for fire suppression on an air carrier aircraft is the flight crew. There is smoke detection throughout the non-occupied spaces on the plane, and nearly every occupied seat is equipped with a smoke detector (the passenger). No one on an aircraft will keep quiet if they smell smoke.
The way the air conditioning system works in a commercial aircraft, light smoke doesn’t tend to travel forward or aft of the source. The air travels circumferentially around the cabin top-to-bottom (register in the ceiling over the aisle, return where the floor meets the fuselage). At most, 3 rows forward and 3 rows aft of the source will smell smoke. That makes locating the source much easier.
The interiors of modern aircraft are very limited in their combustibility, any fire that does develop will usually move slowly enough that the cabin crew can put it out with fire extinguishers or other liquids on board (bottled water, coffee, soda - seriously). In the meantime, the pilots are looking for the nearest suitable airport to land. On the way down, they are talking to someone like me to discuss what is going to happen when they stop - taxi to the terminal or evacuate on the runway - all based on what is being found in the back. The system works surprisingly well - how often do you hear of an interior, in-flight fire on a commercial aircraft?
Cargo aircraft, on the other hand, lack the highly motivated and self-preserving smoke detectors of passenger aircraft. Cargo aircraft have smoke detection throughout the cargo hold(s). All of the larger cargo aircraft can depressurize the cargo hold to slow a fire, then land and have the firefighters on the ground put it out. FedEx has a fire suppression system on some of their international aircraft where landing quickly isn’t an option. The system drives a piercing tip down from the ceiling into the cargo container that is on fire and floods it with compressed air foam. As I remember, they started installing them in 2008 or so, I don’t know if one has actually been used in an onboard fire.
*ABC/ammonium phosphate dry chemical is what is inside of nearly every dry chemical fire extinguisher in the US. Just keep it away from aircraft.