No one has yet mentioned surgically implanted explosives. You could carry more than a twat's worth. You'd need a mechanical or chemical trigger to avoid electronics-detection. Think: punch yourself 6 cm left of the scar, to push the plunger.
Yeah, there have definitely been cases of surgically implanted drug smuggling, so surigcal explosives wouldn't be surprising either. A good plastic (haha) surgeon might be able to implant 10lbs or more, easily enough to bring down a plane. Breast implants would be the obvious place to put it, because they certainly can't open up every woman who wants to get on a plane with "augmentation" so what can you do? Even if they CAT scanned every passenger, and breast implants showed up on the scan, what could they do about it? "We're going to have to cut you open and take a sample of that breast material." This is starting to sound like an Austin Powers sequel... Except unfortunately this could be a grim reality, not a joke. I remember reading about a drug smuggler who was stopped because his legs were "unusual" looking. They opened them up and found out that the purpose of his trip was "business". The solution to this problem might be greater use of high-speed trains, video conferencing, and other things to make air travel less necessary.
What does airport 'security' do about those sneakers that flash upon heelstrike?
They should be seized and destroyed by the fashion cops.