The U.S. Air Force is developing a new, 2nd generation, ten ton large, low air burst bomb. It will replace the older "Daisy Cutter" 7.5 ton bomb developed during the 1960s. This was a 7.5 ton bomb using a semi-liquid explosive for clearing landing zones in the Vietnam jungle. The terms "Daisy Cutter" actually comes from the four foot probe at the bottom of the bomb which triggered the explosion without creating a crater (helicopters don't like to land in craters.) The probe was later replaced with a radar altimeter fuze, but the nickname "Daisy Cutter" stuck. The official designation was BLU-82 (or "Big Blue"). Until the BLU-82 came along, the biggest non-nuclear explosion obtainable was with a FAE (Fuel Air Explosives). FAE  works by dropping a bomb that is actually a large aerosol dispenser. When the FAE "explodes" it first dispenses a large cloud of flammable material (anything like gasoline or propane will work). The cloud is then ignited and huge explosion results. There's one drawback, the size and density of the aerosol cloud depends a lot on the wind, air temperature and humidity. So the power of the explosion will vary a lot. But it's difficult to get a FAE to work in a bomb larger than 2000 pounds. The replacement for the BLU-82 bomb, called MOAB (Massive Ordnance Air Burst) simply uses nine tons of more powerful tritonal explosives, rather that 6.3 tons of the  slurry of ammonium nitrate and powdered aluminum used in the BLU-82.  In dry, dusty conditions, the Daisy Cutter produces a mushroom cloud similar to that created by a nuclear explosion (and for the same reason, the sheer size of the explosion creates an upward pull that sends up a "mushroom" of smoke and dust on a column of smoke). In addition to a more  powerful explosion, MOAB doesnt need a parachute, like the Daisy Cutter, but uses a GPS (like JDAM) and an aerodynamic body to detonate the bomb at a precise area. Thus the MOAB can be dropped from a higher altitude (like outside the range of machine-guns and rifles). Like the Daisy Cutter, MOAB is shoved out the back of a cargo aircraft (usually a C-130, but since the MOAB uses GPS and higher altitude drops, the C-17 can probably be used as well.) MOAB is a highly destructive and terrifying weapon. If used in Iraq, it would demoralize any Iraqi troops in the vicinity who survived the explosion. The force of a MOAB explosion is sufficient to knock over tanks and kill any people within several hundred meters of the detonation. After the 1991 Gulf War, the United States started to get rid of it's various FAE weapons. But some were left in the inventory when the Afghanistan came along and the success of Daisy Cutters there, plus the new Russian research in FAE weapons, led to the new American research effort. There may be larger, or simply more powerful, FAE weapons in the works. But for the moment, MOAB, using pretty old fashioned technology, is the biggest non-nuclear bomb around.