Catching an airplane at most major European airports last week was a little like participating in military maneuvers. London's busy Heathrow was boxed by tanks with cannons uncovered and Grenadier Guards in battle kit. Rome's Ciampino had a sandbagged machine gun nest atop its control tower manned by helmeted carabinieri. Armed Jeeps escorted aircraft along the runways of Orly outside Paris, while 850 flics and special riot troopers kept suspicious eyes on passenger traffic inside the terminal. Everywhere from Amsterdam to Athens there were gun-toting guards and behind them, plainclothes marksmen.
The explanation was a fear of terrorism, which...