The second you exclude a group you open an exploit. It is unfortunate for the elderly or young but it needs to be done. Items have been found in a child's Teddy Bear. What's to say that elderly person is actually elderly and not a disguise (it is an extreme though but possible).

GradGirl, you are correct on one point (and only one). Aviation is not the only sector of interest but because there is a barrier between the public side and air side it is easier to do the screening. Your suggestion to end screening is naive and dangerous. You can't give up one form of security to move on to another area.