Where does a carrier like Singapore Airlines (SIA) park 'idle' airplanes until the current slack in air travel and cargo business picks up again?

Try a desert.

SIA announced last month that it is slashing its capacity by 11 per cent and has grounded a total of 18 planes.

The airline has a fleet of 120 planes. It reported a 43 per cent drop in quarterly profit recently.

Aviation experts say the current bust in air travel and cargo business has led to a boom for owners of what has been called 'airline boneyards'.

These are aircraft storage facilities in very dry places like deserts, especially in the United States and Central Asia.

Ascend, a global air transport consultancy firm, said that there were about 450 Asian-registered aircraft in storage at the beginning of this year. Over 80 per cent are passenger aircraft.

The last time SIA grounded aircraft was in 2003, after the Sars outbreak, when it took fewer than 10 planes out of service for about six months.

One of the planes now grounded is a B-747 cargo freighter, parked in a desert in the US, where hundreds of other commercial planes are also parked.

SIA declined to say where it parks its grounded jets.

But Captain P. James, president of the Airline Pilots Association-Singapore, told The Sunday Times that many airlines store their planes in Victorville, located at the southern edge of the Mojave Desert in California.

At least one other Asian airline, Cathay Pacific, has two freighter planes parked at Victorville. They will be there till the end of this year.

Cathay Pacific and its subsidiary airline Dragonair carried 101,154 tonnes of cargo and mail in January, down 26 per cent compared to the same month last year.

The US is where the now booming major aircraft boneyard operators are located, mainly in the deserts of southern California, Arizona and New Mexico.

One operator is Evergreen Maintenance Centre (EMC), whose facility in Arizona can handle 400 parked planes.

It has seen a spike in business since October, with at least 165 planes in storage.

Mr Steve Caffaro, EMC's vice-president, told CNN last October that he expected up to 50 more aircraft to arrive in the following three to six months. Clearly, he did not foresee the spike.

EMC's facility spans 648ha, holds three hangars and has a 2km-long runway.

Another major boneyard in the Mojave Desert, north of Los Angeles, expects to have a few hundred aircraft stored by the end of this year, CNN reported.

In the case of SIA, why does it choose the desert instead of, say, Changi Airport, to park its planes?

An SIA spokesman said this is because the dry climate in the desert prevents corrosion of aircraft frames and components.

Singapore has hot but very humid weather.

Cathay Pacific's spokesman told The Sunday Times that prolonged storage in a humid environment is bad for aircraft structure and electronics.

Other factors like the facility's airport and runway accessibility, space availability, maintenance capability, cost and proximity to the airline's maintenance engineers are also considered when deciding where to store such aircraft.

Facilities in the desert charge by the month as opposed to airports which charge daily and even hourly.

The airlines contacted by The Sunday Times declined to reveal how much it costs to use desert facilities.

Air logistics officers said for long-term storage, the aircraft is mothballed, which is a process of wrapping it with special material. The engine inlets, exhaust openings and all other gaps and windows are sealed to prevent sand or dust from entering and all fluids are drained from the plane.

Some airlines like Cathay Pacific have a team of engineers to regularly maintain their parked aircraft.

This includes regular functional exercises of the flight control system and other systems, as well as regular inspection of parts and components such as landing gears, wheels and brakes.

This article was first published in The Straits Times.