Two major European countries are warning citizens about travel to the U.S. following high-profile cases in which American federal immigration authorities detained tourists and U.S. green cardholders trying to enter the country.

Beware of new acquaintances who probe for information or attempt to get your involved in what could become a compromising situation. If you see suspicious activity when you’re traveling, contact the FBI at tips.fbi.gov.

Copenhagen follows two other European countries in beefing up its travel guidance for citizens going to America after a spate of detentions at customs.

The global aviation network has suffered shockwaves after one of Europe’s busiest airports was shut down by a fire-related power outage, with thousands of flights affected and major disruption expected to last for days.

A large fire near London’s Heathrow Airport is disrupting global travel for hundreds of thousands of passengers.

A fire that closed London’s Heathrow Airport has sparked one of the most serious disruptions to air travel in years