I’ve decided to split the speculation concerning the science that may have been involved in the plot into a separate post since it is getting long.
Some experts think that the bomb might have involved TATP, the same compound used by the 7/7 bombers.
While there are several liquid explosives that could be used to bring down an aircraft, chemists believe it is more likely that terrorists planned to mix liquid materials that are not themselves explosive but can be combined into a bomb. The liquid explosives that are sufficiently destructive in their own right to blow up a plane are generally too unstable or too easily detected to be readily smuggled aboard.
A more subtle approach would be to combine two or more liquids that are stable by themselves, but which form a powerful explosive when mixed together. A prime candidate for this would be triacetone triperoxide (TATP), the explosive used by the July 7 bombers. Its two raw ingredients are both liquids, which could potentially be carried on board in sufficient quantities in containers such as bottles of shampoo or contact lens solution.
These could then be mixed in a toilet to make TATP, which is a crystalline white powder. The problem here is that the solid has to be dried before it becomes a reliable explosive. It can also be difficult to detonate, as attested by the failure of the attempted suicide attacks on London on July 21 last year.
The problems of assembling and then detonating an improvised bomb of this sort in an airline toilet could explain why the terrorists targeted so many aircraft. It is likely that many of the devices would have failed, so attacking 10 flights would have greatly increased the chances of blowing up one or two. [Link]
There have also been at least two prior terrorist attacks planes using liquid explosives, KAL 858 and PAL 434. [Details follow after the fold]
In 1987, KAL Flight 858 was destroyed using the explosives C-4 and PLX, the latter of which is a liquid:
PLX, or Picatinny Liquid Explosive, is a liquid binary explosive, a mixture of 95% nitromethane and 5% ethylene diamine. It is a slightly yellowish liquid. It was developed at Picatinny Arsenal during World War II for cleaning of minefields. It was to be mixed just before use. PLX was one of the explosives used to down Korean Air Flight 858. [Link]
More recent was the bomb that killed one passenger on board PAL Flight 434 in 1994 [Thanks Sage]:
On December 11, 1994, Flight 434 was on its second leg from Cebu to Tokyo when a bomb exploded, killing one passenger. Authorities later discovered that a passenger on the aircraft’s preceding leg was Ramzi Yousef, who United States authorities have branded a master Al-Qaida bomber and terrorist. He was later convicted of the first World Trade Center bombing, for which he was sentanced to death by lethal injection. Yousef boarded the flight under an assumed name…US prosecutors said the device was a “Mark II” “microbomb” constructed using Casio digital watches as described in Phase I of Operation Bojinka of which this was a test. On Flight 434, Yousef used one tenth of the explosive power he planned to use on eleven U.S. airliners in January of 1995. The bomb was designed to slip through airport security checks undetected. The explosive used was liquid nitroglycerin, which was disguised as a bottle of contact lens fluid. The wires he used were hidden in the heel of his shoe. At that time, metal detectors used in airports did not go down far enough to detect anything there. [Link]
Operation Bojinka was very similar to the plot that the British claim to have uncovered:
Starting on January 21, 1995 and ending on January 22, 1995, they would set the bombs on 11 United States-bound airliners that had stopovers all around East Asia and Southeast Asia… The bombs would have been timed before the operatives stepped off the planes. The aircraft would have blown up over the Pacific Ocean and the South China Sea almost simultaneously. If this plan worked, several thousand would have perished, and air travel would have been shut down worldwide for days, if not weeks. The U.S. government estimated the prospective death toll to be about 4,000 if the plot had been executed. [Link]
Right now, the only method of detection of any potential explosive precursors seems to be the old fashioned taste test:
Liquids were banned, except for baby formula and prescription medicines, and travellers were being told to be prepared to show that these were harmless by tasting them at the security gate. [Link]
