Wired has this article about a 747 that has been converted for fighting fires. Sounds like a joke, but this is real.

A company spent $50 million converting a 747 into a fire fighting aircraft. It can drop 75,000 litres of flame retardant on fires. That compares very favorably with the 4,500 litres that the normal fire drop planes can carry.

Size isn’t the only innovation. Normal air drops on fires rely on gravity to expel the water for fire retardant. That means you get one drop and then have to go back for more.

This bad boy has a special pressurized system that allows for several drops. That helps when you’re carrying such a huge payload.

The major disadvantage of course is that this monster isn’t as nimble or flexible as the smaller aircraft and helicopters.