Aviation Engineer Explains Why Liquids Over 100ml Get Confiscated, But Duty-Free Drinks Don't
Aviation engineer Poo Nisara explains why the 100ml liquid ban exists on planes: a 2006 terror plot to detonate bombs using chemicals hidden in soft drink bottles prompted the global restriction, while duty-free purchases bypass it due to s
On May 7, aviation engineer Poo Nisara explained the reasoning behind the "no liquids exceeding 100 milliliters on aircraft" regulation and answered a long-standing question many travelers have: why does homemade water get confiscated while drinks purchased in duty-free shops can be carried on board?
She shared that during her years working at airports, she frequently encountered frustrated passengers forced to discard expensive perfumes, nearly-empty cosmetic bottles, or souvenirs like homemade chili paste. The turning point for global aviation security occurred on August 10, 2006. That morning, passengers worldwide could still carry water on flights, but within hours, airports globally simultaneously announced a ban on all liquids without prior notice.
The catalyst was British intelligence agency MI5's arrest of 24 alleged terrorists plotting to simultaneously detonate bombs on 10 aircraft over the Atlantic Ocean using dangerous chemicals hidden in soft drink bottles to be mixed onboard. This event became a watershed moment for global aviation security measures.
Regarding why even nearly-empty bottles get seized, X-ray machines don't assess the actual liquid volume remaining but rather the "size of the container." Air gaps inside bottles can cause density calculation errors and may hide dangerous items.
The 100ml figure relates to physics: at 35,000 feet, aircraft fuselages experience constant pressure like an inflated balloon. Calculations show that an explosion from roughly 100 milliliters of liquid might only dent the aircraft's aluminum walls but wouldn't rupture them.
Historical incidents prompted stricter measures. In 1994, chemicals hidden in contact lens solution exploded on an aircraft, but the blast wasn't severe enough to cause critical damage. In 2016, chemicals concealed in a laptop passed inspection, but fortunately detonated when the aircraft was still at lower altitude, allowing most passengers to survive.
The question most travelers ask is why water from home cannot be carried onboard but drinks purchased in duty-free shops can be. The answer lies in "security screening procedures." Products sold in duty-free areas undergo stricter inspection than outside areas to confirm safety before reaching passengers.
From an airport worker's perspective, Poo admits feeling sympathetic whenever she sees passengers lose items at security, but she also finds reassurance that these measures help all travelers reach their destinations safely.
