Members of France’s elite intervention squad are already riding undercover on some trans-Atlantic flights, while a continent away, Mexican security agents also began boarding planes before a new U.S. directive to foil foreign terrorists. Many airlines around the world have said they would cooperate with the U.S. order announced Monday to put armed law enforcement officers on certain international flights as part of a heightened terror alert. Some others say they have used armed marshals since shortly after the Sept. 11, 2001, terror attacks. Full Story