The suicidal pilot who destroyed a Texas office complex has revived the post-9/11 fears that terrorists flying small planes, possibly loaded with extra fuel or explosives, would be almost impossible to stop from carrying out devastating attacks.
"It's something that has exposed a weakness we've seen since 9/11 -- airplanes can fly into buildings," Rep. Michael McCaul, R-Texas, said Thursday just hours after A. Joseph Stack flew his single engine plane into a seven-story Austin building, reducing it to a smoldering wreck.
After Sept. 11, 2001, the federal government stepped up security at all the nation's airports, focusing primarily on commercial aviation. But general aviation – non-commercial, non-scheduled – flights face less screening.
McCaul, a member of the House Homeland Security Committee, plans to raise the issue with his colleagues, but says "no amount of security can prevent a man in a plane from taking his own life."
At dozens of small airports around the country, private pilots with licenses and their own planes are able to fly under the radar – often literally. Pilots flying at low altitudes under so-called visual flight rules are not required to file a flight plan.
And planes weighing 12,500 pounds or less – like Stack's Piper PA-28 – are also exempt from several Transportation Security Administration mandated security screening, such as crew background checks and pilot license reviews.
In the days after 9/11, many small airports enhanced their security by installing higher fences and controlled gates, but the immensity and impracticality of securing so many little airports, pilots and employees was soon apparent.
TSA spokesman Sterling Payne told ABC News the agency is aware of risks posed by general aviation and is continuing to develop new security initiatives and policies.
All licensed U.S. pilots are "recurrently vetted" against government watch lists, Sterling said in a statement. The agency also has an Airport Watch Program and a 1-800 number through which small airport managers can submit security concerns to TSA.
But at many general aviation facilities, airport staff are often the only line of defense against drunk or deranged pilots from taking to the cockpit.
"We do watch for suspicious looking people," said Charlotte Bain, manager of the Brownwood Regional Aiport, 150 miles southwest of Dallas, which sees 20 to 25 flights a day. But, she says, pilots there can largely come and go as they please.
"The Austin attack was a guy who lost his marbles," Bain told ABC News. "We're not going to say no one's allowed to fly their plane now just because of that… it would be sad that one person's idiocy causes everyone to have to pay."
Several aviation experts agree that limits to general or business aviation may not be the answer, and that the Austin attack, while tragic, is of a type difficult to prevent.
Expert: No Easy Fixes to Prevent Small Plane Attacks
"People can hijack a taxi cab, trailer truck, anything," said Purdue University's Vahid Motevalli, who studies security threats posed by general aviation and very light jets. "[We could] set drivers of all trucks that carry fuel to have background checks, but there's only so much you can do."
"For the one guy that did this, there are thousands of people with airplanes and access to planes… but we do need to figure out ways to identify higher-risk situations."
Motevalli has proposed requiring private and business jets to be equipped with tamper-proof GPS devices that can track low-flying planes and correlate their location with electronic flight plans at all times. If a plane were to deviate from course, an alert would notify controllers.
Another option: lowering the weight limit of planes that subjected to TSA guidelines to include light jets, which can fly faster and potentially do more damage if they crash than slower propeller-powered planes. "If a small jet deviates from course and appears to be a threat, you have very little time to do anything," he said.
"I don't know if shoulder-fired missiles should be placed atop every federal building," he said, "but beyond that, protecting high-value potential targets" may be impossible to do.