Terrorists clever enough to use hijacked airliners as missiles and who are not afraid of dying could dare do just about anything. All your suggestion would do is produce a list of untold thousands of potential targets. Without the resources to safeguard all of those targets, you'll find the military and security personnel floundering due to information overload.

Better intelligence to their actual plans would be wonderful, but that has proved difficult to achieve. Some of them, like Abu Nidal, are extremely paranoid. He reportedly tortured and killed hundreds of his own followers because he suspected some were betraying him. Our intelligence agencies reportedly used his own paranoia against him by feeding him rumors. It's rather hard to infiltrate organizations like that.

One of the intelligence failures that lead to Sept 11th was a failure of imagination. Despite some intelligence indications that someone somewhere might someday use an airliner as a weapon, no one seriously thought it would happen and try to take precautions. Odds are none of the precautions would've stopped the attacks, though. There were several thousand airline flights per day in the US alone pre-911. Who besides the hijackers knew which flights on which day were targeted? They used box cutters to take over the plane, but security at the time allowed people to carry box cutters and even small knives on planes. Who knew?