According to new TSA guidelines, starting January 22, 2018, residents of nine states will need a U.S. passport to board any flight, domestic or international.
The nine states are Kentucky, Maine, Minnesota, Missouri, Montana, Oklahoma, Pennsylvania, South Carolina, and Washington.
Each of these states do not currently issue a state ID that lives up to federal ID minimum security requirements, according to the REAL ID Act of 2005.
That means these states have about three months to make changes to their state IDs or drivers licenses so that they meet federal government standards.
Otherwise, you'll need to apply for or renew a passport or just use the one you currently have before passing TSA and getting on a commercial airplane to another U.S. city.
Other forms of ID that will work are permanent resident cards (green cards) or military IDs.
Forbes reports that some states are in the process of updating their ID situations before January 22, so that you might not need a passport to fly.
Check with your local government for updates.
It also looks like even more states will fall under the TSA's flight restricted category by 2020.