In late 2009, the U.S. Air Force, citing cost concerns, threatened to kill the program in favor of a cheaper alternative.

2009年年底，美国空军以成本为理由，威胁要消灭该方案，以廉价的方案来替代。

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For one thing, the fossil fuels will run out eventually. But air capture could provide an ingenious alternative.

首先，地球上的化石燃料最终将会用光，而空气捕捉可能可以提供一种绝佳的替代品。

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On May 24th the OECD launched its alternative measure of well-being which includes 20 different indicators across 11 sectors in its 34 member countries, from life satisfaction to air pollution.

5月24日，经合组织(OECD)发布了衡量幸福的一种替代性方法，其中包括在其34个成员国中横跨11个方面的20种不同的指标，从生活满意度到空气污染程度。

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In addition to alternative fuel, Air Canada will also use other techniques and measures it has adopted to reduce the flight's environmental impact.

ENGADGET: Air Canada embarks on its first biofuel-powered flight from Toronto to Mexico City

He said his corporation arranged for the Renda shipment as an alternative to shipping fuel by air.

WSJ: Fuel Arrives, but Alaska's Deep Freeze Endures

But many small satellite operators say Pegasus is priced out of their reach, and Virgin Galactic believes its air-launched alternative could be made significantly cheaper.

BBC: Science & Environment