Back in the day, before the Terrorists made it impossible to do, I used to always pack a brown-bag lunch.

I'd make a sandwich and freeze it! Turkey breast and similar cold-cuts, and cheese would freeze and thaw well. (Omit the lettuce and tomato).

I'd back it with a frozen juice box, and a frozen container of of yogurt. (Not frozen yogurt, but a frozen container of Yoplait, etc.)

After about 4 hours, everything would be at the right temperature to eat, and I probably won't get food poisoning from things sitting out at room temp. for too long.

It would be great if some vendor inside security were to sell frozen food that would thaw and be ready to eat in 4 hours, or at least frozen juice boxes (or even just ice packs) so you can safely store a sandwich you brought from home. It's especially important for people on special diets. Oh well. We all have to compromise in the name of Security!