When Charles Bishop ignored the frantic gestures of a Coast Guard helicopter pilot and steered his small plane directly toward the Bank of America tower in Tampa, Fla., he exposed a vulnerability the nation still faces.
The teenager's suicide mission shows that even a nation on "high alert" isn't always able to stop people determined to turn an aircraft - or any other vehicle - into an engine of destruction.
Indications are that the youth saw his awful mission as a gesture of support for the terrorist attacks on Sept. 11. But he also showed how difficult it is for the US military, acting in its capacity of homeland defense, to prevent such incidents - despite new rules that permit fighter jets to shoot down a civilian airplane in the name of public safety.
As it turns out, two military jets scrambled from the Homestead Air Force Base in Florida to stop Bishop. But they arrived too late to play any role - underscoring the fact that the military does not provide blanket protection from internal air attack.
For some Americans, Bishop's strike at the 42-story Bank of America building forces an uncomfortable recognition of the potential threat posed by more than 200,000 privately owned planes nationwide, known as general-aviation aircraft.
"Short of grounding all general-aviation aircraft, there's not much that could be done [to stop such people]," says Clint Oster, an aviation economist at Indiana University in Bloomington.
As of this writing, the Federal Aviation Administration has no plans to impose another round of restrictions on the $20 billion general-aviation industry. But as experts at the FBI, the National Security Agency, and the Office of Homeland Security investigate the incident, that could change.
Immediately after Sept. 11, general aviation was shut down, along with the commercial airlines. There was particular concern about security at the almost 20,000 airports - most of them mom-and-pop operations - that handle private planes.
Some are no more than fields with airstrips. Others are surrounded by chain-link fences. Planes sit mostly in the open on the tarmac and could be easy to steal.
But the Aircraft Owners and Pilots Association (AOPA) has argued that even if terrorists got hold of a small plane, the damage they could inflict would be minimal. AOPA spokesman Warren Morningstar contends the Florida crash over the weekend reinforces that. "This is a tragic situation, and certainly we feel very badly for the people involved," he says. "It illustrates what we said: that general aviation does not present much of a threat."
Still, when the skies opened after Sept. 11, restrictions remained on private pilots for almost three more months. Even now, private planes are restricted from flying in certain airspace, such as around Washington.
Dave Claxton, a private pilot, says restrictions change often, which makes it difficult for pilots to be sure they're doing the right thing. "For a while ... you couldn't fly within 12 or 13 miles of a nuclear-power plant," he says. "But there are nuclear-power plants that some people don't even know are there."
Concern about inadvertently violating restrictions is heightened by the fact that private planes now share airspace with military jets. Since Sept. 11, F-15 and F-16 fighter planes have patrolled US skies in numbers unseen since the 1950s, and are on alert at 26 bases where they can be in the air within minutes.
Rules are clear for military, commercial, and private pilots in dealing with such a situation. Fighter pilots approach commercial airliners, try to reach them by radio, and move their wings in the direction they want the commercial plane to follow. If no one responds, force may be authorized, says Col. Don Quenneville, commander of the 102nd Fighter Wing, based at Otis Air National Guard Base in Massachusetts.
But the ability to shoot down a suspect aircraft depends on whether military jets are in the air at the time of a problem, says Maj. Gen. Claude Williams, Virginia National Guard's adjutant general. "It depends on what you've got in the air or if we have to scramble to it."
The response will also depend on whether the threatening aircraft is over a city, where harm to people on the ground from a shot-down plane may be greater than the harm the plane could cause if it hit its target. "The whole area of collateral damage would be taken into account by headquarters," says Col. John Dwyer of the New Jersey Department of Military and Veterans Affairs.
Identifying an aircraft as a threat can also take time, and military commanders say they're careful before authorizing the use of force. "There is a time factor in making sure we don't make a mistake," says General Williams.
"We're not going to be able to provide 100 percent security for the US," he adds. "We can do the best we can to react to these situations."