Small planes are not required to have TSA screening. There are flights in Alaska from ANC to smaller outposts that do not have any screening at all. Just a walk from the waiting area to the plane. An upstart was trying to sell PDX-SEA commuter flights with a similar appeal.
After clearing immigration and customs at IAH on Monday I walked up to the TSA screening and didn't have to show any ID to get through. That was a new one for me.