I didn't even hear any planes except a couple of westbound commercial airliners that habitually use this air shaft to fly over.

除了几架照例飞越这座通风井的向西飞去的商业航班之外，我甚至未曾听到其他飞机的声音。

That's the height that most commercial airliners fly.

这可是如今多数商业航线飞行的高度。

This height is also the frequent cruising altitude of commercial airliners.

这一高度也是商务航线的常用巡航高度。

Put another way, the depth of the Challenger Deep is roughly the same height that commercial airliners travel.

换言之，这一深渊挑战者跟民航客机的飞行高度大致相同。

Five. The highest anyone has ever flown in a hotair balloon is 68,986 feet, nearly twice the cruising altitude of commercial airliners.

世界上乘坐热气球飞行的最高高度是68986英尺，接近商用客机的巡航高度的两倍。