traveller already shopworn and weary from long spells sitting on planes and stand in gate lines can still muster up enough energy to croak about restrictive drome security measures . Shoes and knock have to issue forth off ( unlessyou have TSA PreCheck ) . Laptops are slid out from their cases ( again , for those without PreCheck ) . Unopened bottleful of water are tossed in thriftlessness bins .
For a way of transportation that can cause dehydration , not allowing piss bottles through security is particularly eat into . The directive was put in piazza by the Transportation Security Administration ( TSA ) in 2006 . TSA agents and rider are expected to follow the“3 - 1 - 1 ” rulefor liquid . Those embarkment planes can carry 3.4 ounces of liquid per container in a 1 - quart travelling bag , with one bag per passenger . While the pattern has lent itself to unfavorable judgment and ridicule , intelligence information agencies believe they had — and keep to have — a very salutary reasonableness for instituting it .
What was Operation Overt?
In the 2018 Netflix seriesTerrorism Close Calls , former Central Intelligence Agency ( CIA ) officials go on record with details of a phone number of potentially catastrophic attempts to target civilian that were thwarted by natural law enforcement . Among those person contributing to the show is Steve Hersem , the former lieutenant director of the CIA ’s Community HUMINT ( Human Intelligence ) Division . In 2018 , Hersem evidence Mental Floss that the liquid state forbiddance has ancestor in two separate terrorist plots .
“ The banning of a certain quantity of liquidity from airline flight in 2006 was the unmediated event of the intelligence uncover during Operation Overt , ” Hersem said . Operation Overt was the term used to report a collaborative feat to thwart the plot of land of Abdulla Ahmed Ali , a British citizen who had known tie-up with radical Islamists andterroristshe link up with during frequent trips to Pakistan .
“ Ali ’s cup of tea were on the Q.T. searched when he returned to the UK and a powdered orange soft beverage along with a large number of batteries were found in his suitcase , ” Hersem enjoin . “ Based on his association in Pakistan and the items in his baggage , a layered surveillance program was establish by MI5 , with assist from the London Metropolitan Police . The surveillance , which admit underground cameras and listening devices in Ali ’s apartment , resulted in the discovery of a bomb calorimeter - pull in laboratory and the fleshing out of a phone number of co - plotter . ”

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At one power point during their surveillance , police detective witnessedAli drilling a hole in a soft drink bottle so it could be satisfy with an explosive liquid while still appearing to be unopened . If their program had gone through , Hersem said the answer could have been an tone-beginning on seven woodworking plane wing out of London and head for North America using , among other things , a hydrogen hydrogen peroxide - base - liquid explosive . ( Ali and several of his associateswere convictedand doom to life imprisonment in 2009 . )
But that was n’t the only justification law enforcement used for the liquids ban . “ Al Qaeda had been fixated on targeting aviation as early as 1994 when Ramzi Yousef , the nephew of Khalid Sheikh Mohammed , the mastermind of the 9/11 attack , tested liquid explosives on an aircraft during the Bojinka Plot , ” Hersem said . “ The Bojinka Plot targeted , in part , Philippine Airlines Flight 434 from Manila to Tokyo , which result in the dying of a rider and a large fix being created in the aircraft . ”

The subsequent liquids banning on flights may have stemmed like a shot from Operation Overt , but there was also a X of intelligence to substantiate Al Qaeda ’s ambitions — a threatthat does n’t seem to be letting up . “ The proscription is ongoing because intelligence agency continues to inform the United States Intelligence Community and other confederative intelligence information services that Al Qaeda , its affiliate , and the Islamic State of Iraq and al - Sham , or ISIS , continues to place aviation , ” Hersem sound out .
Why can you only bring 3.4 ounces of liquid through airport security?
But why permit a little over 3 ounces ? According to the TSA , restrain containers to what can fit inside a quart - size of it bag prevent what former TSA administratorKip Hawley once calleda “ critical diam ” to bollocks anything up . The size of the container precludes enough of a potentially explosive liquid from being carried on board .
If you really want to get that bottled water past the security checkpoint , there is a workaround : Just freeze it . TSAallows for frozen liquidsso long as they ’re completely solid . ( If it ’s bathetic or half - melted , you ’ll be asked to thrash it . ) Alternately , you’re able to also just bring acompletely empty bottlethrough and satiate it up once you ’re done with the screening , which is the more environmentally conscious thing to do .
commodious ? Not really . But Hersem maintain it ’s necessary . “ As long as there [ are ] ideologically driven terrorist who are concerned in direct civilian aviation , these type of bans have to be in place and are beneficial in the aggregate . ”

A version of this story to begin with run in 2018 ; it has been update for 2023 .