If well maintained, modern jets have a safe working life of some 30 years, but older planes will inevitably be less fuel-efficient than the latest models.

维护得好的话，现代飞机可以安全服役大约30年，但是老飞机不可避免地将会比最新款的飞机油耗更没效率。

youdao

Boeing and Airbus already are offering a new generation of larger jets built from fuel-saving lightweight composite materials instead of the ARJ21's traditional metals.

波音和空客已经生产出新一代更大型的喷气机，采用了省油轻质复合材料，而非arj21所采用的传统金属。

youdao

In perhaps the most symbolic divestment, JAL will retire its entire fleet of Boeing 747-400 wide-body jets, ageing and fuel-thirsty aircraft that have become too expensive to fly.

其中最具象征意义的资产剥离计划或许是，日航将淘汰旗下所有的波音747 - 400宽体客机，这些耗油且日益老化飞机的飞行成本，已变得过于高昂。

youdao

Today's passenger jets are already something like 75% more fuel efficient than the jets of the early 1960s, and the physics of flying imposes a low ceiling on further advances.

WSJ: The Problem With Going Green by David Owen

Airline gas mileage has improved over the years, the result of filling more seats on each flight, replacing multiple trips on small planes with fewer trips on larger aircraft and replacing older planes with newer, more fuel-efficient jets.

WSJ: How Airlines Spend Your Airfare

The plane represented a big bet on new technology for Boeing: The plane's lightweight frame was to be built using mostly carbon-fiber composites, and it was to have an enhanced electrical system to power more systems and use less fuel than other jets.

WSJ: The Two Men Behind the 787