There's no way to send "someone with a fire extinguisher" to a cargo hold of a modern commercial airliner while in flight (Edit: limited access exists in some a

There's no way to send "someone with a fire extinguisher" to a cargo hold of a modern commercial airliner while in flight (Edit: limited access exists in some airliners, still not something you want to crawl through with a fire extinguisher). The holds do have fire suppression systems, but modern batteries pack a lot of energy, and the extinguishers might not be sufficient. Plus, the holds are literally crammed full, further hindering any firefighting efforts.