Why do third-party sites sometimes show different carry-on rules than the airline?

Third-party aggregators update less frequently than airline websites and sometimes simplify or misreport rules. Always verify against the airline's own baggage or cabin bag page before you travel.

Does my carry-on allowance depend on which fare I bought?

Yes. Many airlines tie carry-on access to fare type. Ryanair's basic fare allows only a small personal item; only Priority and above get overhead bin access. Always check which allowance your specific fare includes.

On a connecting flight with two airlines, whose rules apply?

Each airline's rules apply on its own operated flight. If your connection is on a different carrier, you are subject to that carrier's baggage policy for that leg, regardless of what the issuing airline allows.

What does CarrySizer.com cover?

CarrySizer maintains verified carry-on size and weight rules for over 120 airlines, updated regularly with source links so you can cross-check against the airline's own page.

Is there a government tool for checking what I can bring on a plane?

In the US, the TSA operates a 'What Can I Bring?' search tool at tsa.gov. It covers prohibited and restricted items but does not cover airline-specific size or weight limits.

How to Check Airline Carry-On Rules: The Right Way

Airline carry-on rules are not universal. They vary by carrier, by fare type, by booking class, and sometimes by route. The wrong information at the wrong time costs you money at the gate — or means your bag doesn't travel at all. Here is how to find the right rules every time.

Why Rules Are Harder to Find Than They Should Be

Airlines change their baggage policies regularly, often without announcement. A rule that was accurate six months ago may no longer apply. Third-party travel sites — comparison tools, travel blogs, OTA booking platforms — update less frequently than airlines do, which means they often lag behind by months.

The only authoritative source for any airline's current carry-on rules is the airline's own website.

Step 1: Go Directly to the Airline's Website

Do not rely on:

Google snippets (they pull from cached third-party sources)
OTA booking sites (Expedia, Kayak, Skyscanner)
Travel blogs (accurate at time of writing, not necessarily now)

Do use:

The airline's own baggage or cabin bag page
The airline's FAQ or help center
The airline's manage booking portal (sometimes shows your specific allowance)

To find the right page, search: "[airline name] cabin baggage" — for example, "Ryanair cabin baggage" or "Emirates cabin bag." Most airlines have a direct URL like [airline].com/baggage or [airline].com/travel-information/baggage.

Step 2: Check Which Fare You Booked

This step is where most travelers go wrong. Many airlines now link carry-on access to fare class, not just to the airline's general policy.

Airline	Basic fare	Mid / standard fare	Premium fare
Ryanair	Personal item only (40 × 20 × 25 cm)	Same	Priority: + overhead bag (55 × 40 × 20 cm)
easyJet	Small cabin bag only	Standard: + large overhead bag	Plus: + large overhead bag
American Airlines	Basic Economy: personal item only	Main Cabin: full carry-on	First/Business: full carry-on
Spirit Airlines	Personal item only	Big Front Seat: + carry-on	N/A

If you booked a sale fare or basic economy ticket, assume you have the minimum allowance until you confirm otherwise.

Step 3: Understand Codeshares and Connecting Flights

A codeshare is when one airline sells seats on a flight operated by another. The rule is simple: the operating airline's baggage policy applies on that flight, not the issuing airline's.

If you booked through British Airways but your connecting flight is operated by Iberia, Iberia's carry-on limits apply for that leg. If those limits are tighter, you need to comply with the tighter standard.

For connections booked as a single itinerary, check the rules for every operating carrier involved.

Step 4: Verify Alliance Membership (But Don't Rely on It)

Star Alliance, Oneworld, and SkyTeam airlines tend to have similar baggage frameworks — for example, elite status on one Oneworld carrier typically gets you carry-on upgrades on partner carriers. But each airline sets its own specific dimensions and weight limits. Alliance membership is a useful starting point, not a definitive answer.

Tools That Help

CarrySizer.com — This site maintains verified carry-on size and weight rules for 120+ airlines, with source links to the airline's own policy page. Use it for a quick lookup, then click through to confirm on the airline's site directly.

TSA "What Can I Bring?" tool (tsa.gov) — Covers security-restricted items in the US (liquids, electronics, weapons). Does not cover size or weight rules — those are airline-specific, not TSA-regulated.

IATA Timatic — For visa and document requirements by nationality and destination. Not relevant to baggage, but useful for the same pre-trip research session.

How to Stay Current

Airline carry-on rules change most often after:

Fleet changes (new aircraft with different overhead bin sizes)
Policy updates from low-cost carriers adding unbundled fees
Seasonal enforcement crackdowns (particularly summer and December)

If you fly a particular airline regularly:

Subscribe to their email newsletter (policies are often announced there before the website updates)
Follow the airline's official social media account
Set a bookmark to the airline's baggage page and check it a week before every trip

The five-minute check before each trip costs nothing. A gate fee for an oversized bag can cost $50–100 and a lot of stress.