Abdulmutallab then passed through a walk-through metal detector and put his shoulder bag through an X-ray screening machine, Demuren said.

CNN: Obama orders review of flight screenings

Demuren said the suspect underwent regular screening -- walking through a metal detector and having his shoulder bag scanned through an X-ray machine.

CNN: STORY HIGHLIGHTS

He told Australian media the prospector had been using a state-of-the-art metal detector, which meant he was able to find the gold relatively deep underground in an area which had been searched many times in the past.

BBC: The gold nugget found in Ballarat

"The archaic system of an X-ray machine and metal detector cannot pick up other potential threats posed by passengers, " Baum says.

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More than 3, 500 Anglo-Saxon artefacts were discovered by a metal detector enthusiast in a farmer's field in Staffordshire in July 2009.

BBC: Staffordshire Hoard X-rayed by Birmingham museum

When your name was called, you were passed through a metal detector and ferried upstairs to an undecorated 6-by-6 cubicle.

CNN: We Work For You!

Although that is two to three times the cost of a metal detector, it is less than the price of the fancy explosive-sniffing equipment that is the main rival technology being developed for detecting metal-free mines.

ECONOMIST: Landmines

The rest present them as a voluntary secondary security option in lieu of a pat-down, which is protocol for those who've repeatedly set off the metal detector or have been randomly selected for additional screening.

CNN: Airport security bares all, or does it?

Saudi officials believe that the prince's assailant exploded the 100-gram device using a detonator with a chemical fuse, which would also not be detected by a metal detector.

CNN: Analysis: Similar explosive on plane used in Saudi attack