Brush fires and forest fires get going pretty good most times by strong winds in the area.
These strong winds carry burning leaves, small pieces of brush and even flaming twigs for quite a way before they settle in and light a new fire ahead
of the original one.
Your idea of explosives is interesting, but it would probably blow flaming debris all over heck and gone and the fire would be re-lit and even
bigger.
Granted, depriving the fire of oxygen would cause the fire to go out, but on the outer edges of the fire not enough oxygen would be deprived and
you'd have flaming material launched by the explosion.
As well as, by the time you got there with a bomb, even a large one like a Daisy Cutter and determined the area was clear, it would be too late for an
explosion to make much of a difference.
One of the problems with brush fires is that they've been tightly controlled for the last 35-40 years and there's a lot of unburned fuel out
there.
Better in most cases to let it burn and in fact in Southern California controlled burns have been done to get the fuel - brush etc. - burned down so
the fire can't advance as it wishes.
A bit of a checkerboard burning so to speak.
Problem with a 747 would be maneuvering in the canyons where brush and forest fires are.
The water or retardant drop would be so high that it may not do much good.
Dissipation is the problem here and dropping thousands of gallons of water that's not much more than a fog when it reaches the ground where the fire
is won't do much good.
I've been involved to an extent in SoCal brush fires and watching the fixed wing aircraft do retardant drops is to witness some amazing and very
brave flying.
Best thing for a property owner to do is keep the brush cleared back from the property.
Fire resistant roofs - steel shingle, cement or adobe tile shingles or the old standard, asphalt shingles along with stucco'd exteriors go a long way
toward saving a house in a brush fire area.
Late 60's or so a lot of homes in a Santa Barbara, California canyon burned to the ground.
Most of the ones that burned had wooden shake shingle roofs.
What was amazing was seeing them rebuilt with wooden shake shingle roofs.
I used to use wooden shake shingles as kindling to start the fire in my fireplace, so it kinda makes a guy wonder....