Countries in the program such as Britain and France that have many citizens who have traveled to Iraq and Syria will have to allow more U.S. air marshals on flights and step up data sharing.
WASHINGTON — The Department of Homeland Security has toughened air-travel requirements on foreign governments in response to what it believes is the growing threat from fighters who have gone to Syria and Iraq to join the Islamic State and other extremist groups, senior U.S. officials said Thursday.
The changes will be applied to the so-called visa-waiver program that the United States has with 38 countries.