Will I be able to purchase airline tickets before my passport is renewed?

My passport has expired and I am in the process of renewing it. I plan to fly to Switzerland in May 2011 and would like to know if I will be able to purchase

Source: http://www.us-passport-service-guide.com/will-i-be-able-to-purchase-airline-tickets-before-my-passport-is-renewed.html

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