On the morning of Thursday, August 10, 2006, Steven Lancaster woke to the breaking news of arrests: British terrorists had allegedly planned to explode up to 10 passenger planes bound for the United States over the mid-Atlantic using liquid bombs, hiding the components of each bomb inside their carry-on luggage. He knew immediately what he had to do. "I had my development team go out and get a bunch of liquids, and I said, 'OK, I need you to be able to tell one apart from all the others.'"
Lancaster is a vice president of Guardian Technologies International, one of several companies working with the federal Transportation Security Laboratory (TSL), where new technologies that may improve airport security are tested against actual explosives and not just safe substitutes. Currently, the most serious security gap is the ease with which explosives—including liquid ones—can pass through airport checkpoints. Guardian is developing PinPoint, a software system that can analyze X-ray images of carry-on bags for telltale signatures of dangerous substances. By mid-August, the software could recognize seven types of solid explosives, but it had not yet been trained on liquids of any kind.
Lancaster's team returned from the local Safeway with about a dozen bottles of innocuous liquids: water, Coke, Diet Coke, Neutrogena Hand Sanitizer, Gerber baby juices, and more. Guardian has dozens of ready-packed carry-ons in its testing lab, and for the rest of the day the team packed the bottles of liquid in among clothing, electronics, and cans of tennis balls, then ran them repeatedly through the lab's X-ray machine. At random, they picked Nestea Sweetened Iced Tea as their "target." By the following morning, Lancaster says, they had succeeded. Whenever the (admittedly harmless) Nestea went through the machine, PinPoint would highlight it on-screen with a big red box and display a message urging the operator to "Open Bag." Even Lipton iced tea did not trigger the same response.
This past summer, the government's scramble to find technology that can identify specific liquids led many people to conclude that liquid bombs are a new threat. They are not. In 1987 a liquor bottle filled with liquid explosives, placed in a carry-on bag in an overhead bin, helped terrorists crash a South Korean airliner. All 115 on board died. In 1994 Al Qaeda member Ramzi Yousef, an architect of the first World Trade Center bombing, detonated liquid nitroglycerin that he had brought on board a Philippine Airlines flight in contact-lens solution bottles. The explosion killed one passenger and injured several others. This was just a test run for a much larger plan to explode a dozen U.S.-bound passenger jets over the Pacific, according to prosecutors. In 2002 the FBI issued a nationwide advisory that Al Qaeda had discussed sneaking liquid explosives disguised as coffee onto planes. This past March, NBC News leaked details of a classified investigation by the Government Accountability Office that showed homemade bomb-making materials sailing through security at all 21 airports tested.
So what could make us safer? As Lancaster points out, "The technology to detect liquid explosives absolutely does exist today—it's called chemical analysis." For complete certainty, you could chemically test every single liquid carried aboard, which he estimates would take around 10 to 15 minutes per passenger. "You'd have to show up for your airplane 20 hours before it takes off," Lancaster says. The Department of Homeland Security (DHS) has been evaluating 10 new liquid-explosives detection technologies since the spring of 2006, yet these scan only one bottle at a time—and that bottle must be removed from its carry-on. That's not much of an improvement over current methods, in which security personnel swab suspicious objects one by one, then place the swabs in a machine to check for dangerous molecules.
While methods may improve, the big picture is less than reassuring. With limited resources pitted against a seemingly limitless number of ways to produce terror, we will probably always be chasing a moving target. Shoe bomber Richard Reid boarded a Paris to Miami flight in 2001 wearing high-tops packed with explosives, and suddenly all passengers were putting their shoes through the X-ray machines. In the wake of this summer's scare in Britain, the DHS shifted its focus to finding better ways to detect liquid bombs or their components.
It's clear that technology alone cannot solve the problem, and security experts consider the equipment at airport checkpoints to be the last line of defense. The British bomb plot was uncovered not by machinery, after all, but by old-fashioned intelligence work. Furthermore, if checkpoint security becomes too tight, terrorists may simply switch their strategy. Most of the 6 billion pounds of commercial cargo that fly with U.S. passengers each year is never checked for explosives, and airline personnel may also load explosives directly onto a plane. (One member of the recent plot was a Heathrow employee with extensive security clearance.) Terrorists equipped with surface-to-air missiles, like the ones fired at an Israeli-chartered Boeing 757 in Kenya in 2002, never need to pass through any security checkpoints.
