An airdrop is a type of airlift, developed during World War II to resupply otherwise inaccessible troops, who themselves may have been airborne forces. In some cases, it is used to refer to the airborne assault itself. Early airdrops were conducted by dropping or pushing padded bundles from aircraft. Later small crates with parachutes were pushed out of the aircraft's side cargo doors. Later cargo aircraft were designed with rear access ramps, lowerable in flight, that allowed large platforms to be rolled out the back.
As aircraft grew larger, the U.S. Air Force and Army developed low-level extraction, allowing tanks and other large supplies to be delivered, such as the M551 Sheridan or BMD-3. Propaganda leaflets are also a common item to airdrop.
The airdropping of weapons evolved to the concept of having the payload itself as one massive bomb. The 15,000 pound (6,800 kg) BLU-82, nicknamed the "Daisy Cutter" for its ability to turn a dense forest into a helicopter landing zone in a single blast, was used in Vietnam and recently in Afghanistan. The 22,600 pound (10,250 kg) GBU-43/B, nicknamed the "Mother Of All Bombs", was deployed to the Persian Gulf for The Iraq War. These palletized airdropped weapons are used by cargo aircraft like the C-130 or C-17 in the traditional role of a bomber aircraft.
In peacekeeping operations or humanitarian aid situations, food and medical supplies are often airdropped from United Nations and other aircraft.