Only being able to bring liquid containers that are no larger than 3.4oz/100ml in your carry on bags is something that every passenger finds frustrating.

We get it.

Travel-sized containers of your favorite brands aren’t always available, pouring liquids into smaller containers is a hassle, you are very limited in what you can bring if you aren’t checking in a bag, and purchasing drinks at the airport can be expensive.

However, the reason why you can’t bring liquids on a plane is for your own safety.

The TSA implemented the 3-1-1 Rule because terrorists have previously tried to sneak liquid explosives on a plane on more than one occasion.

The Story Behind Why You Can’t Bring Liquids on a Plane

In 2006, terrorists planned to sneak liquid explosives onto a plane and then detonate them while onboard the aircraft.

Abdulla Ahmed Ali, who had known ties to radical Islamists and terrorists, was a focus of attention for intelligence agencies.

As it was believed that he planned a terror plot against the United Kingdom, he was paid much greater attention to than other passengers.

On one occasion, he flew from Pakistan to England with his bags secretly searched to see if anything suspicious could be found.

Due to a powdered orange soft drink and a large number of batteries being found in his suitcase, a surveillance program called Operation Overt was born.

This was the UK’s largest surveillance operation at the time with 220 officers from Britain’s police, counter-terrorism, military, and intelligence services all involved.

Another man, called Assad Sarwar, was seen buying unusual objects and disposing of a large number of empty hydrogen peroxide bottles at a recycling center.

On one occasion, Sarwar and Ali met at a park, and with evidence mounting that a terror plot was in the works, MI5 secretly entered Ali’s apartment and discovered that it was a homemade bomb making facility.

Because of this, Operation Overt included installing secret cameras and bugging Ali’s apartment, which also led to knowing the identities of a number of co-conspirators.

Another man, Tanvir Husain, was filmed in Ali’s apartment making explosive devices out of soft drink bottles on August 3rd, 2006.

The following day, Ali was seen at an internet café, where he was researching international flight timetables – namely British flights heading to five US cities and two Canadian cities.

The plan was to detonate the explosives as each plane was landing to inflict the maximum amount of damage over the crowded cities below as the planes crashed.

On August 9th, the British police arrested 24 suspects, including Sarwar, Ali, and an undercover officer who infiltrated the group and warned that an attack was imminent.

An immediate ban on liquids aboard commercial flights was implemented, with the decision that only bottles of liquids containing 3.4oz/100ml could pass through airport security coming shortly later.

This rule has remained to this day.

Why Can You Only Bring 3.40z/100ml on a Plane?

3.4oz/100ml of liquids in each container is the permitted amount because it is the maximum amount of liquid explosives that pose little to no risk to travelers.

This number didn’t come out of nowhere.

Tests by explosives and terrorism experts in the USA, UK, and around the world took place to determine what the maximum safest amount of liquids that passengers could carry onboard would be.

Related: What Size Liquid Can You Take on a Plane?

Bringing Liquids On a Plane

Carry on Bags

If packed in your carry on bags, you are only allowed to travel with containers of liquids that are no larger than 3.4 ounces and are placed in a 1 quart-sized resalable bag.

This amounts to a maximum of about 7-8 travel sized containers.

There are a few exceptions, which we list below.

Checked Bags

Generally, there is no limit to how many ounces of liquid containers you can pack in your checked bags.

However, the TSA state that there is a limit on “the total amount of restricted medicinal and toiletry articles in checked baggage”.

This includes items like nail polish, nail polish remover, perfume, cologne, hair spray, hair texturizer, and makeup remover.

For these items, “the total aggregate quantity per person cannot exceed 2 kg (70 ounces) or 2 L (68 fluid ounces”).

The capacity of each container must not exceed 0.5 kg (18 ounces) or 500 ml (17 fluid ounces).

Domestic vs. International Flights

It makes no difference if you’re flying domestically within the USA or internationally.

You are only allowed to bring 3.4oz/100ml of liquids on a plane in your carry on bags.

They must also be placed in a 1 quart-sized resalable bag.

Exceptions to the 3-1-1 Rule

Despite very tough security measures, there are several exceptions to the 3-1-1 Rule.

The following items, many of which are deemed essential, are allowed to exceed 3.4oz/100ml.

  • Breast milk and formula
  • Baby food
  • Liquid medication
  • Hand sanitizer
  • Jumbo disinfecting wipes
  • STEB items (secure, tamper-evident bags purchased at the airport)
  • Cough syrup
  • Gel-filled bras
  • Saline solution
  • Ice packs (must be frozen solid)

Just keep in mind that if you plan to take any of the above items, they should be removed from your carry on bags for additional screening.

How to Bring More than 3.4 oz / 100ml on a Plane

Besides the exceptions to the 3-1-1 Rule listed above, there is a loophole that lets you bring more than 3.4oz/100ml on a plane in your carry on.

If you are traveling with a baby or young child, you can say that the liquid is for them.

Of course, you are quite limited with what liquids this will work with.

Water bottles and juice will be fine, but trying to get alcohol past airport security will be a no-go.

Containers Larger Than 3.4 Oz/100ml Will Be Confiscated

If you try and bring a liquid, gel or aerosol container that exceeds 3.4oz/100ml through airport security, a security agent will confiscate the item.

This isn’t just limited to personal care products, either.

So if you want to bring coffee on a plane, you won’t be able to.

Liquids That Are Forbidden on Planes

There are some liquids that, even if under 3.4 oz/100ml, you are forbidden from bringing them on a plane.

Liquids that are forbidden include:

  • Bleach
  • Most flammable liquids (you can bring nail polish on a plane, though)
  • Most toxic liquids
  • Aerosols that do not qualify as toiletries
  • Alcoholic Beverages over 70% ABV (140 proof)
  • Fertilizer
  • Insecticide

5 Surprising Items That Qualify As Liquids

There are some items that you wouldn’t expect to qualify as liquids, but actually are.

So, keep the following items in mind next time you travel:

Ella Dunham, a Freelance Travel Journalist and Marketing Manager, boasts an impressive career spanning eight years in the travel and tourism sectors.

Honored as one of "30 Under 30" by TTG Media (the world’s very first weekly travel trade newspaper), a "Tour Operator Travel Guru" and "Legend Award" winner, Ella is also a Fellow of the Institute of Travel, a Member of the Association of Women Travel Executives, has completed over 250 travel modules, and hosts travel-focused segments on national radio shows where she provides insights on travel regulations and destinations.

Ella has visited over 40 countries (with 10 more planned this year).