New focus on passenger carry-ons

A bomb plot aimed at US airplanes, subverted in Britain Thursday, has dramatized the ongoing terrorist threat to airlines and quickly changed what Americans can carry on board.

The immediate security concern is containers of liquids and gels – which officials suspected might be used to hold substances more insidious than water, contact lens fluid, suntan lotion, or baby formula and which a terrorist could mix on board to create a powerful explosive. As a precautionary measure, the US Department of Homeland Security Thursday barred passengers from carrying most liquids into the cabins of commercial carriers.

But bottles of liquids are only one challenge posed by carry-on luggage, and some security analysts say stiffer restrictions governing hand-carried items are urgently needed.

"The new threat is from hand luggage," says Michael Greenberger, director of the Center for Health and Homeland Security at the University of Maryland. "It's now the task of counterterrorism experts to deal with this new threat, but I think it's possible [that] for a considerable amount of time liquids will not be allowed on planes."

Some airline experts say the more intensive screening of hand luggage may shift the way many Americans fly. Toiletries such as hand sanitizers, aftershaves, deodorants, and mouthwashes will not be allowed in carry-on luggage. "It basically forces people to check their bags," says David Stempler, president of the Air Travelers Association. "That adds time and the risk that the bag does not get to your destination."

Restricting hand-carried luggage is a difficult decision for officials. Many American travelers do not check their bags anymore, because they have connecting flights or they don't want to wait in line. People who travel with young children need to have on hand either special formulas or the kids' favorite drinks.

"Security officials must balance out the security question in conjunction with the ease of travel," says Frank Ciffullo, director of the terrorism task force at the Center for Strategic and International Studies. "But we also have to insert new measures all the time to keep the adversary on edge."

The new travel rules were instituted because terrorists are always adapting, says Mr. Greenberger. "Terrorists know they can't use shoe bombs because the wires stick out, so they are going to try to do something that foils traditional screening devices."

Stepped-up screening is a good thing, says Mr. Stempler. "The TSA has done a good job of checking for explosives on checked luggage," he says. "Now we need to increase screening for carry-ons."

At press time, investigators hadn't revealed details about the explosives the suspects planned to use. But Homeland Security chief Michael Chertoff said during a press conference that they'd planned to board with "liquid-explosive ingredients and detonating devices disguised as beverages, electronic devices, and other common objects."

One candidate explosive could be triacetone triperoxide (TATP), says Neal Langerman with the American Chemical Society's division of chemical health and safety. In recent years, antiterrorism experts have noted the growing use of peroxide-based explosives – a cocktail of readily available liquids such as acetone, highly concentrated hydrogen peroxide, and other components. TATP, for instance, reportedly carries 80 percent of the explosive punch of TNT.

According to analysts at Jane's Information Group in Britain, TATP's use has grown in response to improved methods for detecting high explosives that the military uses. TATP was found in the "shoe bomber's" sneakers in 2001. Terrorists who detonated bombs in London last summer also used TATP, according to Jane's.

Many travelers seemed to take the changes in stride. At the international terminal at Boston's Logan Airport, Earnest Mazique, a graduate student at Emerson College in Boston, said his worst fear – that officials would take his laptop computer – was not realized. "I did repack my bags this morning [to remove liquids from carry-on luggage]," he said. As for worries about flying Thursday, he added, "I'm concerned. They say if you change your schedule, the terrorists win. I've got a funeral to get to, so I've got to get on the plane." Laptop in hand, that's what he did.

• Matt Bradley and Peter N. Spotts in Boston and Lauren Dake in New York contributed to this report.