Likewise some airlines don't even require someone to fly. I knew someone that would ship very expensive camera gear to film productions directly with an airline. They would check the cases and send it off. Someone would just go and pick it up. Obviously only really works if you're not dealing with customs.
I thought terrorists had done the "check your bag and don't board" thing enough for it to be disallowed. But maybe this story took place a long time ago?
Many (most?) large airlines take cargo directly like this. It's not so much "check your bag and don't board" as it is "consign this cargo shipment" which happens to be taken on the same aircraft as passengers and their luggage. Unlike checked luggage you need to declare the contents of the packages etc., and presumably there is security screening.
TSA has limits and they’re pretty strict with wanting to know what’s being shipped. You can’t even ship over a pound without being subject to background checks and approval.
https://www.deltacargo.com/Cargo/