But despite a series of episodes in recent years that have targeted transportation hubs worldwide, security experts predict that the latest attacks will revive — but not resolve — a thorny public debate about the benefits of ever more costly and intensive screening systems meant to identify terrorists among the millions of people who travel each day.
“It’s always about achieving a balance between what is achievable and what is practical,” said Norman Shanks, a consultant and former manager of airport security at Heathrow Airport near London.
It's neither achievable or practical. If people want to blow themselves up or are willing to get caught, you just can't stop them. Maybe you can stop them from blowing up a plane. You can't stop them from killing people. And here you don't even need to know how to build a bomb, you just need a local gun dealer.