Shampoo, iPods and Starbucks lattes have suddenly become security threats.
Terrorists could easily slip a few apparently innocuous items past airport security and assemble them into a lethal explosive once aloft, security experts said.
Some envision a group of two or three terrorists mixing up explosives in an airplane bathroom, perhaps even using commonplace materials such as hydrogen peroxide and detonating their bomb with the battery from a cellphone or some other small electronic device.
"In mid-flight you could go into the toilet, attach the mobile phone to the explosives and, as the plane makes a final approach over a densely populated urban area, you detonate it," said Irish security analyst Tom Clonan.
To puncture an aircraft's fuselage would require an explosive charge "half the size of a cigarette packet", he said.
Experts inter viewed after Thursday's arrest of suspects in a massive airline bomb plot say there are many ways that seemingly innocuous substances could be smuggled aboard a plane and assembled into an explosive device in flight.
That means airport security screening, now focused on detecting weapons and large amounts of explosives, might have to ban such workaday items as cell phones, hand sanitizer and contact lens solution.
Flying could become an experience of extreme privation from the conveniences of modern life, preceded by even more onerous security screening.
"That theatre we see, of people taking off shoes, is not going to stop a suicide bomber. The terrorists have already sniffed out the weak spots and are adopting new tactics," Clonan said.
Officials declined to discuss whatever technology the thwarted plot uncovered. But British authorities banned all carry-on luggage, suggesting that the explosives or their ingredients would have been difficult or impossible for airport security screening to detect.
In the United States, hand luggage was still being allowed, but liquids were banned except for baby formula, insulin and other medicines.
"We are taking the step of preventing liquids from getting into the cabin to give us time to make adjustments in our current screening tactics, based upon what we learn from this investigation," US Homeland Security Secretary Michael Chertoff said on Thursday morning.
Experts said the measures suggest that terrorists planned to sneak one or more bomb ingredients aboard as many as 10 aircraft, then mix and wire them to a battery detonator.
"Their intention was to smuggle on board some kind of liquid explosive disguised as an aftershave bottle or hair conditioner or shampoo or whatever," said MJ Gohel, who is director of the Asia-Pacific Foundation, a London-based think tank.
A similar threat in January 1995 led officials in the Philippines to briefly ban aerosol sprays, bottled gels and liquid containers of more than about an ounce (28 grams) from departing planes because of a suspected terror plot during a visit by Pope John Paul II.