[magicalhippo]

Some years ago I was flying home, and it turned out someone had called in a bomb threat. So, naturally, they had ramped up the security scan to the max, causing a massive queue.

The landside area was packed to the brim with travelers waiting in line, mixed with the people on their way to check-in pushing their trollies loaded with suitcases.

I've never been so scared, waiting in line for security, as I imagined how easily anyone could pack 6-7 huge suitcases filled with explosives onto a trolley in the parking lot right outside, move into the packed crowd without suspicion and set it off.

No need to get on a plane.

[TylerE]

Don't need an airport for that. Any busy city sidewalk would do just fine.