Another reason for the increase in bird strikes is the growing popularity of air travel in the United States.

VOA: special.2009.04.01

Somehow, if you could manufacture a really smooth frictionless surface, that if you took a hockey puck or something and an air cushion and you give it a push, in some idealized world, it'll travel forever.

如果你制造一个绝对光滑无摩擦的表面,然后在上面放个冰球或者别的什么,或者气垫,然后推它一下,在理想条件下,它会永远运动下去

耶鲁公开课 - 基础物理课程节选

The United States halted air travel for three days after the terrorist attacks in two thousand one.

VOA: special.2010.04.23

The air travel agency is currently testing a radar system at the international airport in Seattle,Washington.

VOA: special.2009.04.01

At its worst, the crisis affected nearly a third of world air travel.

VOA: special.2010.04.23

Other businesses that depend on air travel, including hotels and vacation places,also suffered.

VOA: special.2010.04.23

But he says, it's because of current wind patterns that the volcano is having such a major affect on European air travel.

VOA: standard.2010.04.16

Experts say bringing this technology to commercial air travel is a dream far in the future.

VOA: standard.2010.08.11

It has also disrupted air travel with many flights in Europe either delayed or cancelled.

VOA: standard.2009.12.21

Aircraft consultant Richard Aboulafia says while air travel appears to be making a comeback, demand for first class tickets remains sluggish and airline revenues are well below 2008 peak levels.

VOA: standard.2010.03.30

He says the substances are especially dangerous because they travel through the air and stay in the atmosphere, soil and water.

VOA: special.2009.06.23

He will now travel to Oulu,Finland for the Air Guitar World Championships starting August nineteenth.

VOA: special.2009.08.14

Some travel guides have described Luxor as the world's largest "open-air museum."

VOA: special.2011.03.08

"At a per-passenger-mile basis, rail is about three times as efficient as travel by car, in terms of fuel efficiency, and six times as efficient as travel by air, so there are pretty substantial pollution reduction benefits both in terms of greenhouse gases and other pollutants."

VOA: standard.2010.02.15