Some day soon, any terrorist who tries to use an airliner in an attack will find himself holding a useless weapon. At least that's the goal of a handful of inventors who are trying to work out a high-tech shield against hijackers.
With the experience of September 11 behind them, aviation security experts are working on ways to short circuit a similar attack. One proposal would let a technician on the ground take remote control of an airplane in mid-flight. Another gives pilots a "panic button" that would activate an on-board computer and force the plane to land at the nearest airfield. And then there's the project known as "Soft Walls."
"As the aircraft approaches a no-fly zone, the pilot will feel as though there's some external force pushing the aircraft away. And if the pilot counteracts the force, then the force will eventually get strong enough to prevent the aircraft from entering the no-fly zone," said Edward Lee, the project leader.
The computer software engineer based his invisible walls on software already in use aboard many commercial aircraft - the so-called "Ground-Proximity Warning System." The system keeps track of the plane's location, speed, altitude and rate of climb or decent to warn pilots of approaching hazards, like other planes, mountains or the ground. Mr. Lee says, in the most modern passenger jets, which already use computers to turn the rudder and manage other flight controls, a new layer of software can turn that warning into a flat refusal to cooperate. If a pilot tried to fly over restricted airspace, for example, the plane would steer itself away.
That sounded good to one passenger at Los Angeles International Airport. "Technology's probably going to be the savior. Hijacking and so on, like I said, it's since the late '60s, it's been going on. Software to stop this from happening, it's probably gonna have to go that way," he said.
But if federal air safety officials approve a plan like Soft Walls, it could be years before it's in place. For one thing, most planes in use today are steered mechanically, not by computer. Mr. Lee says his team at the University of California, Berkeley could incorporate the system into more common auto-pilot mechanisms, which keep a plane on course while the pilot attends to other tasks. But nobody knows how long that would take or what it would cost.
Duane Woerth, president of the Airline Pilots Association, worries about putting too much faith in high-tech solutions. "Anything we test or certify to put in the airplane has to assume that that item, that electronic component, that hydraulic component at some point for the wrong reason, at the worst time, will fail," he said. "So all our checklists, all our procedures, anticipate that, and we have to have the ability to overcome that mechanical, that electronic failure."
As an example of what can happen when people place too much faith in machines, Mr. Woerth points to HAL, the homicidal computer in the movie 2001, a Space Odyssey.
Engineer Lee says arguments like that underestimate the reliability of machines. "HAL was actually far more human than computer-like, and in fact the kind of behavior that HAL exhibited is far more typical of human beings than computers," he said. "Human beings are actually not such reliable creatures and can yield to their own random behavior."
He notes that computers, integrated into automotive design, have made cars much safer and more dependable than they used to be.
Even if the Soft Walls concept does clear the objections of pilots, it could be years before it's ready to take to the skies. In the meantime, officials are building up an array of ground-based systems, ranging from more screening officers to check passengers' luggage to computerized fingerprint databases that will seek to identify terrorism suspects before they can board a plane.