A plot to blow up planes in flight from the UK to the US and commit "mass murder on an unimaginable scale" has been disrupted, Scotland Yard has said. It is thought the plan was to detonate explosive devices smuggled in hand luggage on to as many as 10 aircraft. Police are searching premises after 21 people were arrested. Home Secretary John Reid said they believed the "main players" were accounted for.

Several readers have pointed out new restrictions imposed as a result of this plot on passengers' carry-on luggage. Hand luggage allowances have been stripped back to little more than wallets, travel documents, verifiable prescription medicines, contact lenses or glasses, essential baby items, female sanitary items, tissues (unboxed). Food and drink, other than baby milk, has also been banned. Parents, apparently, must "verify" baby milk by tasting it in front of security staff. Keys are allowed, but NOT electronic types, including remote car locking types. All electronic items - laptops, ipods, phones, etc - are verboten and must be stashed in suitcases.

The crackdown on electronic items has fuelled speculation that the plot could have involved some kind of remote detonation, using a mobile phone or electronic car key for example, or some kind of device that would be assembled once on the air plane. At the same time, the ban on liquids suggests authorities suspect the alleged plot involved some type of liquid type explosive. Unsurprisingly, the additional security measures are causing massive delays, with some flights being cancelled.