The aircraft had reached its cruising altitude of about 39,000 feet.

那架飞机已经达到了大约三万九千英尺的巡航高度。

《柯林斯英汉双解大词典》

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。

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He told me how I could get the plane back up to cruising altitude after he'd parachuted out over the ocean.

他告诉我可以在他跳伞后把飞机调回坠毁所需的角度。

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During the demonstration flights, a pilot handled the takeoff and climb to cruising altitude.

FORBES: Pilot-Optional Flight Is Closer Than You Think

Once the A380 reached cruising altitude, passengers were free to walk around both decks to explore the amenities.

FORBES: Magazine Article

Once at cruising altitude I dialed in an economy fuel setting of 53 gallons per hour at a true airspeed of 390mph.

FORBES: Magazine Article