Isn't that the job of the communications tower at the airport? I don't think the twin towers had comms marra
They were massive skyscrapers dominating the skyline. I imagine once the hijackers saw this huge target they pointed the nose down at target and the rest was history. They didn't need to consider passenger safety, whether the aircraft could take the strain of the descent/turns or anything like that, it was just a case of lining it up and flying straight. I refuse to believe any pilot couldn't do that.