Flights should be confirmed 48 hours before departure.

航班应在起飞前48小时予以确认。

《牛津词典》

Two hours before departure time.

起飞前2小时。

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And it's a good idea to see your dentist before departure.

最好在出发前先看看牙医。

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White House officials are sticking to a prediction they say is based on conversations with congressional Democratic leaders, that a vote in the House of Representatives can be achieved before the president's scheduled departure March 18 on a trip to Guam, Indonesia and Australia.

VOA: standard.2010.03.10

The survey also tested booking tickets just five to 15 days before departure in April.

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Just before departure, customers are driven to planes in their choice of either a Mercedes-Benz or a Porsche.

WSJ: The Tarmac Express: A Porsche to the Plane

Visitors are recommended to submit applications no later than 72 hours before departure in case further inquiry is necessary.

CNN: U.S. visa rules explained