New travel document requirements have been put in place.  Recently, Department of State and Homeland Security announced a “Western Hemisphere Travel Initiative”  is requiring that  all US Citizens to have a passport for entering or re-entering from outside the US by Air travel need a passport.

There is an exception if cruising in and out of the same U.S. port.  A valid drivers license with your picture and Original Birth Certificate would be allowed.  However, if for some reason you had to take a flight back to the U. S. or one to start the cruise out of the county you will need a passport.  I do not recommend using a birth certificatre4.

In addition, no mater where you are traveling and are using a passport the expiration of the passport can not be 6 months before the return.  Another way to say this is that the passport must be good for 6 months after your return.

I highly suggest any travel outside the U. S. that a passenger should have a passport.

Passports are alot easier to obtain and most local US Post Offices can take the picture, fill out and send in the application to the nearest Passport Office. You will, however, need your Original or Certified copy of you Birth Certificate to get the passport for the first time. Passports are valid for 10 years for adults, five years for children because their features change so quickly.

For more information go to  the official Government website.
http://travel.state.gov/travel/cbpmc/cbpmc_2223.html