PJ Vogt

Fully plastic guns never became a real threat, but what terrorists really did increasingly develop were bombs that used less and less detectable metal.

In 1994, Ramzi Youssef, the mastermind of the first World Trade Center bombing, hides liquid nitroglycerin in a bottle of contact lens solution.

The bomb blows up, killing one person aboard a flight.

And the methods that terrorists use to smuggle these explosives onto flights keep advancing.

In 2001, the shoe bomber, Richard Reid, smuggles 10 ounces of non-metal explosive material in his shoes, which nearly works, except he is stopped while struggling to light his shoes, these putzes.

After that, for decades, we have to take our shoes off so they can be x-ray scanned for hidden plastic or hidden liquids.

In 2006, terrorists in England try smuggling lots of explosive liquid in multiple plastic bottles.

They're caught, but that gets us our no liquids over three ounces rule.

Finally, in 2009, we see the terrorist who, in my opinion, has most successfully contributed to making our airport experiences more annoying.

The underwear bomber, Umar Farouk Abdul-Muttalib.

When Abdul-Muttalib boarded his Christmas Day flight from Amsterdam to Detroit, the bomb he was carrying was a packet of powder sewn into the crotch of his underwear.

Undetectable by metal detectors and unlikely to be detected by a TSA agent, since searching passengers' crotches by hand was not a part of security.

Abdul Muttalib got on board with his bomb, but now he had to light it, which is where things went wrong for him.

Somehow, instead of detonating his crotch, he ended up setting his legs on fire.

A fellow passenger noticed Abdul Muttalib was restrained.

Tragedy was averted.

But now this new hole in the fence had to be patched.

The TSA needed a way to look into people's underwear in as unobtrusive a manner as possible, a very hard engineering problem to solve.

Which brings us back to Doug McMakin and the machine he helped develop.

Millimeter wave technology, essentially a real life version of the X-ray specs that used to exist only in science fiction.