With the new airline restictions (much needed) what is to stop someone from renting a private plane or buying their own corporate jet and reeking havoc like the tragic events of last week?
Scale. Skyscrapers have been hit by small planes before. The damage is nothing like what you saw. Companies will be careful about renting large planes to people that don’t know.
Keep in mind the the WTC did not go down due to the plane crash, but due to the fire from the planes’ fuel. Smaller planes, and even many large ones, don’t have that fuel load.
The use of Sky Marshals is the only effective security restriction being used. The rest are meaningless gestures to make it look like a lot of action is being taken.
AFAIK, the hijackers did not crawl down into the cargo hold to get weapons. So what difference does it make if you turn in your checked baggage at the hotel, offsite parking lot, or airport curb side? Checking baggage at the terminal counter would not have stopped or even worried the hijackers.
Some of those hijackers took the trouble to learn to fly the planes. It will still be no trouble for one of them to get a job in the airport. Look at all the restaurants and bars located past security. The people working there have knives for cutting fruit, vegetables, meat, etc, even if the customers don’t. The deliveries come in boxes, so there may even be box cutters.