After 9/11, cockpit doors were sealed, air marshals were added and airport searches became more aggressive, all to make sure an airliner could never again be used as a weapon. Yet little has been done to guard against attacks with smaller planes. That point was driven home with chilling force on Thursday when a Texas man with a grudge against the IRS crashed his single-engine plane into an office building in a fiery suicide attack. One person inside the building was also killed. "It's a big gap," said R. William Johnstone, an aviation security consultant and former staff member of the commission that investigated the Sept. 11 attacks. "It wouldn't take much, even a minor incident involving two simultaneously attacking planes, to inflict enough damage to set off alarm bells and do some serious harm to the economy and national psyche." 

It goes without saying that an airliner pilot couldn't do the same thing despite the air marshals and searches. How do we know. Because they don't mention it in the article ...