It was a different kind of terror plot, as devious as it was dangerous.
The terrorists wouldn't board with bombs. They would board with seemingly harmless household ingredients that wouldn't make a security agent blink.
These explosive fluids could pass for hair gel, fit in a tube of toothpaste, and detonate with the flash of a disposable camera.
The potential weapons would be assembled onboard and ignited in an attempt to kill hundreds in one strike.
In this case, the specific plan was to conceal a liquid bomb ingredient - acetone peroxide, also called the "Mother of Satan."
It would be dyed the color of the beverage at the bottom of a drink container.
This peroxide-based explosive is the same substance reportedly used by London subway bombers just over one year ago.
The top of the bottle would contain the original beverage, allowing terrorists to even drink from the bottle if questioned by security.
A co-conspirator on the same flight, another terrorist, would bring the detonator - in this case the filament found in a disposable camera's bulb.
The 24 terror suspects, now in British custody, allegedly planned to set off explosives on up to 10 cross-Atlantic flights, tearing them to pieces midair.
A Threat the Government Could See Coming
This kind of plot may sound new to most of us, but it's a threat government agencies have known about for years.
It's a loophole in security they haven't fixed.
In February 2005, a Government Accountability Office report determined that the Transportation Security Administration had "delayed the development of a device to detect weapons, liquid explosives ... in containers found in carry-on baggage or passenger's effects."
A different report, issued jointly by the FBI and the Department of Homeland Security, noted in its title the "Possible Terrorist Use of Liquid Explosive Materials in Future Attacks."
This report mentioned that liquid explosives could be set off by the filament of a single Christmas light.
Meanwhile, people of every age were waiting in line at the airport, shoes in hand.
This time, however, shoes were not the problem.
U.S. agencies knew there was a threat of liquid explosives for which they weren't prepared.
Despite the billions spent on homeland security since Sept. 11, 2001, America's anti-terror strategy could not keep up with rapidly evolving terror threats.
Thursday's alleged terrorists planned to bring simple travel items onboard their planned flights: sports drinks and disposable cameras.
If their operation had succeeded as designed, it could have struck up to 10 commercial jets, taking almost as many lives as the attacks of Sept. 11.
If the planes had exploded above major U.S. cities, as some feared the terrorists had planned, the loss of life could have been far greater.
Newest Methods of Detection
Enough aircraft explosions have happened in the last few decades that they are now part of the risks associated with flying.
In 1988, 259 people were killed on Pan Am flight 103 just four days before Christmas.
The explosive used was a small piece of plastic called semtex, hidden inside a transistor radio and checked onboard.
Six years later, Ramzi Yousef, the mastermind behind the 1993 World Trade Center attack, detonated a bomb onboard a Philippine Airlines flight, killing a 24-year-old engineer.
The explosive, nitrocellulose, was stuffed in a child's doll and hidden in a life jacket pouch.
Yousef planned to strike again, this time planning to blow up 11 flights over the Pacific in what he called the "bojinka" plot - bojinka means "loud bang" in Serbo-Croatian.
The planned method: to use liquid explosives concealed in a bottle of contact lens solution. But Yousef was arrested in Pakistan, however, and turned over to the United States. He was convicted in 1997 of masterminding the 1993 World Trade Center attack and the 1994 Philippine airplane bombing. He is serving a life sentence without parole at the Supermax federal prison in Florence, Colo.
As Yousef's plan showed, it seemed that terrorists' tools were getting smaller, simpler, and easier to disguise.
Then Sept. 11 came.
The explosives were bigger than ever: The weapons were the planes themselves. Airport security got tighter than ever, and flight safety awareness was at an all-time high.
This awareness may have helped when in December 2001, on American Airlines flight 63, as many as 197 lives were saved by onboard passengers and crew.
Together they foiled the plot of Richard Reid, the now-infamous "shoe bomber."
Reid had a plastic explosive in the sole of his shoe, and the fuse was his shoelace.
Flight attendants noticed his attempt to light the fuse, and passengers helped douse him with water and restrain him.
Security again got tighter, and now we all must remove our shoes for inspection before boarding aircrafts.
The most advanced technology to detect explosives is a new trace portal now installed in 33 airports, according to the Transportation Security Administration.
These portals blow puffs of air on passengers and then test tiny particles collected from the puff.
The puff test, however, does not help with liquids - the explosive ingredients that seem to be on the latest frontier of terrorism.
As bombers find new ways to sacrifice their lives while taking the lives of others, security officials have had to constantly adapt to stop them before striking.