Nigeria - this is where the would-be-bomber of the December 25, 2009 attack is from.
Afghanistan - Taliban and Islamic militants are still fighting Western forces in Osama bin Laden's adopted homeland.
Algeria - known to house al Qaeda members.
Iran - has been called a state sponsor of terrorism by the US State Department.
Iraq - long-standing issues that continue post-Saddam Hussein with Islamic militants.
Lebanon - Home of the group Hezbollah, there is a question about whether Lebanon can effectively prevent terrorist activities.
Libya - Is protesting its inclusion in this list of countries which will require stricter security screenings for its airports.
Pakistan - known for housing Taliban members and routine terrorist activities.
Saudi Arabia - homeland of Osama bin Laden and potential al Qaeda presence.
Syria - known as a state sponsor of terrorism.
Sudan - possible al Qaeda members and acts of terrorism in this troubled country.
Somalia - home of al Shabaab, a group with links to al Qaeda.
Yemen - al Qaeda in this country claimed responsibility for the December 25, 2009 attack as the training grounds for the attempted bombing suspect.
Cuba - there has been some noise made about whether Cuba should be included with the other 13 countries on this list.