Sizer rules & enforcement reality (2026)
Sizers aren’t neutral. The same “carry-on size” can be ignored on one flight and enforced aggressively on another. This page focuses on what gets targeted at the gate, and which bag types reduce your odds of getting flagged.
Enforcement risk tiers
Use this as a planning heuristic. The stricter the sizer culture, the more “shape” matters (soft bags win).
| Group | Typical published carry-on | Primary “gotcha” | Risk |
|---|---|---|---|
| US Big Three (UA / DL / AA) | 22 × 14 × 9 (common baseline) | Discretion spikes on full flights; hardshell gets targeted | Medium |
| US ULCC (Spirit / Frontier) | Personal item is the pricing weapon | Sizer culture is the business model (fees are the product) | Extreme |
| Europe LCC (Ryanair / easyJet) | Personal item baseline + paid “large cabin bag” | They monetize enforcement; wearable storage is the classic workaround | Extreme |
| Regional flights (small jets) | Overheads + under-seat are physically smaller | Tags can reroute bags to carousel; under-seat obstructions exist on some aircraft | High |
What triggers checks
On busy flights, agents often pre-tag rigid rollers because they don’t compress. Soft bags get “visual passes” more often because they look smaller and can squeeze into spaces.
Some airports are moving away from obvious metal sizers, which shifts enforcement to agent judgment. If it looks big, you lose the argument before it starts.
Small aircraft have real physical limits. Even if “carry-on allowed,” you may be forced to gate-check. Plan for what happens next: keep medicine/keys on-person if a tag routes to the carousel.
On ULCCs, enforcement is not incidental — it’s revenue. The safest play is choosing a personal item that can compress into the sizer even when slightly packed.
Recommended gear
These are “bag archetypes” designed to survive sizers and gate discretion. Affiliate links, when configured, appear below.
Next: airline-specific tactics
If you want the airline-specific fee traps and hacks, use the “How to beat fees” page for your airline.