Easy to hide, liquid weapon exposes a flaw
As travelers worry about what seems an exotic new terrorist weapon, specialists said yesterday that liquid explosives have been a known threat for quite a while.
Using readily available ingredients, specialists said, terrorists could make a liquid explosive before boarding a plane, or smuggle on the ingredients and combine them in flight -- as authorities say the British suspects planned to do. Then, a flame or spark could be used to set off a powerful blast.
Al Qaeda has eyed liquid explosives to take down commercial airliners for more than a decade. In 1994, terrorists in Asia successfully detonated a liquid bomb on an airplane, killing a Japanese businessman.
Liquid explosives have been used in mining and oil exploration for many decades, and so it was just a matter of time, specialists said, before terrorists would attempt to use them as well. In many ways, liquid explosives are similar to their solid counterparts -- highly destructive in small quantities, made with common ingredients -- but they have the advantage of being easy to disguise. The liquid ingredients are typically clear, but the terrorists could have colored them with dye.
``This is not a new threat," said Neal Langerman , a chemical safety specialist for private industry who is an officer of the American Chemical Society. ``This is just a different form of the same explosive threat we have been dealing with since before Sept. 11."
Still, the London plot exposed a key flaw in American airport security. Arnold Barnett, an aviation-security specialist and professor at MIT's Sloan School of Management, said security measures at US airports before yesterday would not have been sufficient to stop terrorists from smuggling liquid explosives onto a plane. Authorities had not banned most liquid carry-on items -- as they did after discovering the new alleged plot -- because airline security requires prioritizing threats and balancing between safety and the disruption involved in preventing certain kinds of attacks.
Liquids in checked baggage are not considered a threat because the explosive must be detonated by a person, and bags are scanned to detect timers or triggering devices.
Companies are already working on airport scanners to detect dangerous materials within a bottle, though none has been considered ideal for deployment, according to Jimmie Oxley, an explosives specialist and professor at the University of Rhode Island who has done extensive work with the military and federal law enforcement. However, she predicted that the alleged plot would create a strong push for bottle scanners .
British authorities have not said what explosive the terror suspects planned to use, but a memo sent out yesterday morning by US law enforcement officials indicated that it contained the chemical peroxide. One explosive used by suicide bombers in Israel and shoe bomber Richard Reid is made with relatively common liquids, including hydrogen peroxide. Called TATP, or triacetone triperoxide, it would be difficult to make on board a plane, though, because the terrorist would have needed to keep it cold with ice, Oxley said. In Reid's case, he mixed the explosive before he boarded the plane, turning it into a solid, then hid it in his shoes.
In 1995, the United States and the Philippines uncovered a plot by Ramzi Yousef, later sentenced to life in prison for his role in the 1993 World Trade Center bombing, and his uncle, 9/11 mastermind Khalid Sheikh Mohammed, to use liquid explosives to bomb a dozen US airliners over the Pacific Ocean. A year earlier, Yousef planted a bomb beneath a seat on a flight from Manila to Tokyo. The bomb caused minor damage, but killed one and injured 10 others.
Explosive-detection specialists said technologies now exist to detect liquids, gels, or other substances that could be the building blocks of a bomb.
Peter J. Howe of the Globe staff contributed to this report. Bryan Bender can be reached at bender@globe.com, and Gareth Cook can be reached at cook@globe.com. 