A plane can also carry only a few bombs before needing to return to base. Highly accurate cruise missiles can be used, but at nearly a million dollars a shot, they have to be employed sparingly. The US military's stock of air-launched cruise missiles was critically depleted during the Kosovo hostilities. The missiles are also enormously complicated machines and are therefore prone to failure. A reporter from Aviation Week riding along on a B-52 bomber sortie during the conflict reported that all 12 of the missiles his aircraft carried failed to launch.
Artillery is therefore the most prevalent and low-tech approach to bombardment of an area.
The lack of precision is counterbalanced by the sheer number of shells that can be fired in a sustained manner. The new DERA 'smart shell' is quite standard as far as the explosive part goes. The innovation is in the tip. It includes a tiny and very rugged computer and GPS navigation receiver. About 3 seconds after the shell leaves the gun's barrel it uses its GPS equipment to take a reading from any overhead military satellites.