IIRC the US Military has a kind of air burst bomb that is actually kind of simple:
Rupture a canister of compressed propane in the air, let the gas mix with atmospheric oxygen for a few seconds, ignite.
This clip of HULK has an example; the time index for the explosion I’m talking about is 00:45 seconds into the flash video.
A little hard to tell what you’re looking for in the OP, but if its the word for that type of bomb, I believe it’s “thermobaric”
ETA: doh!!
That kind of bomb is called a “fuel-air explosive.” I don’t know if ours use propane; they can also be made with powdered solid fuels.
There’s a lot of talk these days about a new kind of bomb called a thermobaric bomb, which may be a kind of fuel-air explosive. The explanations in the press calling them “vacuum bombs” and such don’t make sense.
I am pretty sure that is a fuel air bomb.
The Russians recently tested a huge bomb of this nature that was widely reported as the “most powerful bomb”.
Too late should not have looked for topical link.
More about the US version: Massive Ordnance Air Burst bomb. There’s some mention and a linky or two about the Russian version, too.
You need a fast connection to download the video, but here’s one about the MOAB: Mother of All Bombs
This is not the same thing as a Fuel-Air explosive. Both make big booms though.
Thermobaric and fuel-air explosives are two different things. Thermobaric explosives are fuel-rich, which results in combustion with atmospheric oxygen after the initial detonation.
http://www.globalsecurity.org/military/systems/munitions/thermobaric.htm
Ah, well… Apologies all around, please go back to what you were doing… 
I believe that FAE weapons have been banned because the enemy may inhale some of the explosive gas before detonation.(its ok to blow them to bits but gassing is a no no)
A pity really because its well useful in cave/tunnel complexes because the explosive reaches round corners and in to nooks and crannies that other bombs dont reach.
News to me, an I would assume I would know. FAEs are legal AFAIK
Yes I wasn’t totally sure but a few years ago there were those who were trying to get it banned .
I’m glad that they didn’t succeed.