Chemicals sitting in anyone’s bathroom at home could be used to make an easily smuggled bomb that would badly damage a passenger jet, and experts have been warning about this danger for years.
The difficult part, experts say, is putting together such a bomb without blowing yourself up.
British police said they foiled a plot on Thursday to blow up aircraft flying between Britain and the United States, and U.S. and British authorities banned liquids, including drinks, hair gels and lotions, from carry-on baggage.
"My hunch is that the reason they are prohibiting this stuff is that it does obviously have the potential of being assembled on board so that it doesn’t look like a bomb going through the X-ray machine," said Alfred Blumstein, a criminologist at Carnegie Mellon University in Pittsburgh who helped write a government report on explosives threats to airlines.
Such mundane items as nail polish remover, disinfectants and hair coloring contain chemicals can be combined to make an explosion and are not detectable by "sniffing" machines, which detect plastic explosives but are not used with all baggage.
Explosive ingredients can be concealed in bottles or other innocent-looking containers that would pass through X-ray machines.
That does not mean they are easy to make into bombs, cautioned Neal Langerman, a San Diego consultant who is former chair of the American Chemical Society’s Division of Chemical Health and Safety.
"Many of the ingredients like acetone are household chemicals," Langerman said in a telephone interview. But some kind of expertise is usually needed to buy peroxide that is concentrated enough to work in an explosive, he noted.
Bombers who attacked London Underground trains and a bus in July 2005 used homemade peroxide-based explosives carried in backpacks.
An explosive chemical called triacetone triperoxide, or TATP, can be put together with sulfuric acid, found in some drain cleaners, hydrogen peroxide, a medical disinfectant and hair bleach, and acetone, found in nail polish remover.
"I would doubt that the average layperson would successfully make TATP without killing themselves," Langerman said.
TATP starts out as a liquid that crystallizes into a white powder. "When they mix it, it detonates," Langerman said.
"When you do that at 25,000 feet in the middle of the Atlantic, you and everybody else die."
And the voltage from any battery, combined with the right detonater, such as a powerful camera flash attachment, could act as a detonator for several chemical explosives, Langerman said in a telephone interview.
Some combinations can be set off using another chemical such as hydrochloric acid, easily carried in a small glass bottle.
Nitroglycerin, a clear yellow or colorless liquid, can produce an explosion sometimes with vigorous shaking.
People have tried several times to use such easily concealed explosives on aircraft. British-born Richard Reid was tackled by passengers in December 2001 while trying to detonate explosives stuffed in his shoes in an aircraft lavatory.
In 1994, Islamic fundamentalists set off liquid explosives on a Japan-bound Philippine Airlines plane, killing a Japanese passenger and injuring 10 others.
Mark Ensalaco, an international terrorism expert at the University of Dayton in Ohio, said Thursday’s foiled operation appeared to be identical to the Japan attack.
"I stress identical with the explosives in liquids, which appear to be assembled on the plane," Ensalaco said in a statement.