On September 11,2001, intermational terrorists hjjacked four commercial airplanes, two of which were used to destroy the twin towers of the world Trade Centerin New York City.

【翻译】2001年9月11日，国际恐怖分子劫持了四架商用飞机，其中两架被用来摧毁纽约市世贸中心的双子塔。

【分析】be used to do：指“主语被用来做某事”。此时，主语往往是表示“物”。

【一言辨异】be used to doing, be used to do, used to do:

The old man used to watch TV in the morning. Now he is used to taking a walk, and his stick is used to support him.

【翻译】这位老人过去常在早上看电视。现在他习惯了散步，他的拐杖用来支撑他。