The 100ml cap persists on both sides of the Atlantic not because the scanners failed, but because US and EU regulators treat the rule as a default that must be actively lifted. The European Commission’s framework permits airports with certified next-generation screening to raise the limit but does not require it. The TSA keeps 3-1-1 as the standing requirement at every checkpoint lacking certified CT lanes.
Europe’s September 2024 snap-back proved how quickly that permission can be withdrawn. A temporary technical issue, not a new threat, pushed the 100ml limit back across the bloc.
Ask a traveler why they still pack 3.4-ounce bottles, and you’ll get the machine answer: the airports haven’t installed the new scanners yet. Convenient. Also wrong, or at least badly incomplete.
The same computed tomography hardware sits in security lanes on both sides of the Atlantic and reads carry-on contents in much the same way. What differs is the legal default behind each rulebook.
In Europe, airports with certified C3 EDSCB equipment may lift the 100ml cap — but only with the European Commission‘s sign-off, and only until Brussels decides to withdraw it. In the United States, the TSA has never abolished 3-1-1.
The clearest proof came in September 2024, when the Commission reinstated the 100ml limit across the bloc. A pullback like that would be unthinkable in a system where hardware alone dictated the rules.
Two regulators, two defaults
The 3-1-1 rule came first, written after a foiled plot to bring liquid explosives aboard transatlantic flights. CT scanners came later, promising something the old 2D X-ray machines couldn’t: a detailed 3D image of a bag’s contents that could distinguish benign liquids from threats more reliably.
But that capability never translated into a single global rule change. The European Commission’s framework permits airports with certified next-generation screening to lift the cap; it does not require them to do so.
The TSA’s posture is different: the agency has never published a formal retirement date for 3-1-1.
Cost is another brake. A CT lane is a capital project, not a swap — the unit is expensive, and the checkpoint usually needs work to house it.
That kind of spending slows deployment on both sides of the Atlantic, leaving a patchwork where the rule can differ from one airport, or one security lane, to the next.
The September 2024 pullback
For a while, some EU airports allowed liquids above 100ml thanks to certified C3 EDSCB equipment. Then the European Commission announced on 31 July 2024 that the cap would return from 1 September. The legal mechanism was Regulation (EU) 2024/2108, which amended the broader 2015/1998 framework.
The Commission described the action as “not in response to any new threat but addresses a temporary technical issue.” The notice named no manufacturer, no scanner model, and no national aviation authority. It didn’t need to.
The point wasn’t who failed; it was that a certification problem alone could suspend the relaxation.
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Why your lane, not your airport, decides
Even at airports with CT scanners, the journey through security can fork. A lane that still relies on older X-ray equipment subjects passengers to the 3-1-1 rule, while the next lane over, running certified CT, may allow larger liquids. The system works that way by design: permission follows the certified machine, not the airport’s name.
The EU framework makes this explicit. C3 EDSCB equipment must carry either full EU Stamp status or EU Stamp pending to support screening beyond the traditional limit, and the Commission holds the power to suspend that status. The 2024 act swept in units that were already marked before 1 August 2024, pulling them back under the 100ml limit.
For travelers, that means no real-time public map or centralized database tells you which lanes at a given airport are currently operating with active CT certification. Lane-level, not airport-level, is the correct unit of analysis.
| Jurisdiction/regulator | Legal status of 100ml cap | Condition permitting lifting | Who certifies or validates equipment | Current status |
|---|---|---|---|---|
| United States / TSA | 3-1-1 remains the standing TSA carry-on screening rule; no verified abolition date found | No retrieved primary source establishes a general automatic exemption for every certified CT lane | TSA | No formal public retirement date verified; checkpoint-specific exceptions should not be generalized |
| European Union / European Commission | The general EU restriction limits individual LAG containers to 100 ml, subject to defined exemptions | C3 EDSCB equipment with EU Stamp or EU Stamp pending status may support screening beyond the traditional limit | European Commission framework, with Member State evidence submitted for equipment compliance | Regulation (EU) 2024/2108 imposed a 100 ml limit on standard C3 configurations from 1 September 2024 |
| European Union / Member States | National authorities implement EU aviation-security requirements at airports | Airport deployment and operation depend on equipment status and applicable EU measures | Member State evidence supports the EU Stamp process; a specific national authority was not identified | Specific national certification arrangements not verified |
| United Kingdom / Department for Transport | At most UK airports, containers above 100 ml cannot pass security | Next-generation screening equipment was intended to permit larger quantities, subject to government implementation | UK aviation-security approved-equipment framework; specific software sign-off body not verified | Retrieved GOV.UK guidance still states that most airports apply the 100 ml limit |
| UK / airports receiving installation extensions | The existing 100 ml rule continued while equipment installation was incomplete | Installation of the required next-generation equipment, followed by permission under applicable rules | Specific airport certification sign-off not stated in retrieved material | Extensions of up to one year granted in April 2024; later reinstatement reported. Complete 2026 list not verified |
| Source: European Commission, Directorate-General for Mobility and Transport; EUR-Lex; UK Department for Transport; Transportation Security Administration (TSA) | ||||
How the EU Stamp process actually works
The EU’s permission mechanism runs through a specific chain: a Member State supplies compliance evidence to the Commission, and the Commission can award, or withdraw, EU Stamp or EU Stamp pending status. The 2024 act also tightened the standard that C3 EDSCB equipment has to meet.
What matters is that the Commission’s power is discretionary, not automatic. Certification alone lifts nothing; the decision sits with the Commission. And as September showed, that discretion runs both ways.
On the US side, the retrieved material holds nothing comparable. The sources do not establish whether the TSA tests scanner software against its own standard, or who signs off if it does. No rule found in the material turns CT certification into an automatic end to 3-1-1.
In Europe, the operative question is whether the Commission has exercised its permission. In the US, it’s whether the checkpoint itself has changed its default, and the rulebook hasn’t been formally retired.
What this means for you
The defensive-travel answer is straightforward: pack to the 3-1-1 standard regardless of the airport’s advertised technology. A full-size bottle of sunscreen that clears a CT lane at one airport can still be stopped at a legacy lane on the next leg. Connections multiply the risk, since your clearance in a CT lane doesn’t transfer to the next checkpoint.
Budget a little extra time at security when rules are in flux, and consider buying liquids airside or checking a bag if you need more than 100ml. The regulator’s permission can be withdrawn with little notice, as Europe demonstrated in September 2024. The only consistently safe default is still the old one.
Key terms
- 3-1-1
- The TSA’s carry-on liquid rule is known as 3-1-1, and it caps each container at 100ml — 3.4 ounces. It has been the standing requirement at US checkpoints since long before CT scanners arrived, and it applies by default rather than by any decision to keep it. That is what makes it different from Europe’s arrangement: in the US, only a particular checkpoint’s own procedures change what a lane enforces.
- C3 EDSCB
- EDSCB stands for Explosive Detection Systems for Cabin Baggage, and standard C3 is the performance level the EU requires of equipment used to screen cabin bags. Under the amended framework, such equipment must meet at least standard C3, and a configuration earns full EU Stamp status or EU Stamp pending status once a Member State submits evidence that it complies. In this article’s story, that standard is the hinge: the equipment was certified, the permission existed, and the Commission withdrew it anyway.
- EU Stamp
- EU Stamp is the marking the European Commission awards to security equipment that meets the EU’s screening standard, while EU Stamp pending covers units whose compliance evidence is still being assessed. A Member State must supply that evidence before the Commission can award or withdraw either status, and the decision is the Commission’s alone. In this article’s case, the marking is what stands between a certified machine and a lifted limit: the hardware can be ready while the permission is not.
- Computed tomography (CT)
- Computed tomography, or CT, is the scanning technology in the newest security lanes, producing a three-dimensional image of a bag’s contents rather than the flat one older X-ray machines give. Regulators treat it as the more reliable way to tell benign liquids from threats, which is why the EU framework ties any relaxation of the 100ml cap to CT equipment that holds the right certification. In this article’s case, the same class of machine sits in lanes on both sides of the Atlantic, which is why hardware alone never explained the gap between the two rulebooks.
Questions? Answers.
Has the TSA put a formal retirement date for the 3-1-1 rule on the record?
No formal public retirement date appears in the retrieved material. Unless a particular checkpoint’s own TSA procedures say otherwise, keep treating the rule as a standing requirement.
What is ‘EU Stamp’ or ‘EU Stamp pending’ status, and why does it matter for liquid rules at EU airports?
EU Stamp and EU Stamp pending are the marking statuses the European Commission can award to standard C3 EDSCB equipment. A Member State supplies the compliance evidence, and the Commission decides whether the equipment may support screening beyond the traditional 100ml limit. The 2024 regulation brought even units that already carried the marking back under the 100ml limit.
Did the UK also plan to drop its 100ml limit, and what happened?
Yes. UK airports were given until June 2024 to install next-generation screening equipment, and the government said the eventual limit would rise to 2 litres. Airports that had already lifted the 100ml cap then had to put it back, after the Department for Transport concluded the systems still needed work.
