What’s more, underneath the top six inches of dirt topsoil is a clay-like sub layer called caliche. This extremely hard subsoil allows the planes to be parked in the desert without the need to construct expensive new parking ramps, according to the 309 AMARG.

Planes are expensive things to build and maintain, but even at the end of their flying lives they still have their uses. But it takes a lot of room – and a lot of money – to store these unused planes in the kind of hangars needed to keep them warm and dry. It’s much cheaper to store them in the kind of conditions found in Tucson. That’s the reason why many of the world’s biggest aircraft boneyards are found in the dry deserts of the south-western US.

But it’s not simply a case of landing a plane at Davis-Monthan, parking it in one of the rows and handing someone the keys. Many of the aircraft are considered inactive, but have to be able to be brought back into service if need be. That takes a lot of work.

Broken bombers

The Boneyard’s workers have an exhaustive checklist. Any planes that have served on aircraft carriers have to be thoroughly washed to get rid of corroding salt. All aircraft have their fuel tanks and fuel lines drained, and flushed with a light, viscous oil similar to that used in sewing machines to ensure all the moving parts are lubricated. Then they must have any explosive devices – such as the charges that activate ejection seats – safely removed. Then, any ducts or inlets are covered with aluminium tape and the aircraft are painted over with a special easily strippable paint – two coats of black, and a final white layer to help deflect the fierce desert sun and keep the aircraft relatively cool.