Helicopters are expensive and delicate machines requiring heavy maintenance, especially when flying in dusty conditions.

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His mechanics now take each plane apart once a year for heavy maintenance.

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Two were in various stages of a heavy maintenance period, and one was in a Refueling Complex Over-Haul (RCOH) period.

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Today, to save money, airlines have outsourced most of their heavy maintenance and repairs to contractors not only in the U.S. but also overseas in China, Mexico, Singapore, El Salvador and elsewhere.

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But a strike by oil workers in Norway and heavy maintenance at North Sea fields has exacerbated the shortage this year and sent the price of Brent for immediate delivery much higher.

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But a heavy schedule of January maintenance at West Coast refineries has led to sharply higher prices there.

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