But the short answer is 49 days before your departure for domestic flights, while the sweet spot for international flights is 81 days.

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Clinton had limited her comments on domestic policy as secretary of state and her departure has freed her to speak more openly about the issues.

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The ideal time to book domestic travel last year was 21 to 35 days before departure and within three months before departure for international travel, according to analysis from Kayak.

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