You'll need a passport.
If Steven Spielberg were to stop you on the street next year and invite you to star in his movie on the condition that leave right now for the airport without stopping at home, your opportunity at fame and fortune would be squandered if you happened to be a resident of New York, New Hampshire, Minnesota, Louisiana, or American Samoa.
The reason: At some point in 2016—the precise date hasn’t yet been announced—driver’s licenses from those states will no longer be considered sufficient to clear airport security and board an airplane.
This new policy is a result of the Real ID act, passed by Congress in 2005 as a counterterrorism measure to standardize the reliability and efficacy of personal identification. Unfortunately, the driver’s licenses of that handful of states did not make the cut, failing to provide enough security features in the cards themselves or enough verification of identity and immigration status in the application processes.
The Department of Homeland Security began rolling out Real ID in 2014. Phase one involved restricted government areas, and phases two and three concerned semi-restricted areas like nuclear power plants. But phase four touches federally regulated aircraft—and therefore will affect millions of people.
When it rolls out officially for travelers, you won’t have anything new to worry about if you’re going abroad—you’ll need a passport anyway. But if you’re flying domestically, double check that your license makes the ID cut.
Update: The State Department has some tips on how to get a passport in a timely manner.