Liquidized gel shoe insoles which will soon be barred from air travel. This is due to the brilliant terrorists who could use these innocent appearing foot savers to mix liquidized explosives. Yellow and Blue could make boom.
The reality is that all footwear should be banned from airlines due to its largely uncategorized appearance. Mere children in these terrorist countries have access to sweat shops, plastic injection molders and explosives. If you add that all together you could have some really wicked customized shoe-bombs. Anything can be hidden inside of a tennis shoe.
The Solution Edit
Sterilized, One size fits all, paper slippers for all passengers, for every flight. All shoes can be left in lockers outside of the airport awaiting round trip passengers on their return. One way passengers, well, who cares about those deserters?