Every site publishes the policy number. Almost none of them say whether anyone checks it. The honest answer is that US airlines have moved in opposite directions — and on two of them, the agent used to be paid per bag they stopped.
United removed the sizer boxes from every gate in January 2020. The internal memo told agents that if a bag “looks like it fits, let it go” and to use their best judgment. Sizers stayed at check-in and at security — the measurement moved earlier, it did not disappear. ReportedOne Mile at a Time
American did the same on 6 October 2025, keeping sizers in the check-in area. Its on-record statement was that the change was made “to further simplify the boarding experience for our customers and team members”, and agents were told to err on the side of the customer on marginal bags. ReportedThe Points Guy
For Delta, Southwest, Alaska, JetBlue, Hawaiian, Breeze and Sun Country we found no reliable public information either way, so we are not going to tell you. Every site that confidently lists gate-sizer status for all eleven carriers is filling in the gaps.
A US Senate Permanent Subcommittee on Investigations report published in November 2024 found that Frontier and Spirit paid over $26 million in incentive payments to gate agents and other personnel across 2022 and 2023 to enforce bag policy. Frontier personnel could earn up to $10 for each bag a passenger was forced to check at the gate. Government reportUS Senate Permanent Subcommittee on Investigations
The subcommittee warned the payments “may inappropriately encourage abuse of discretion… potentially forcing customers to choose between paying an unjust bag fee or missing their flight.” Government reportUS Senate Permanent Subcommittee on Investigations
Frontier publicly confirmed the programme. It said it incentivises staff “to ensure compliance with the bag size requirements to ensure all customers are treated fairly, including the majority who comply with the rules.” ReportedThe Hill
Frontier also measures the personal item against a dedicated smaller box: a personal item “must fit within the smaller sizer box”, checked during boarding. Airline’s own wordsFrontier, quoted by One Mile at a Time Allegiant charges specifically for oversized personal items as a separate category. Airline’s own wordsAllegiant
Spirit ceased operations on 2 May 2026 and is not listed on this site. It appears here only because the Senate report documented the two carriers together.
Free — the bins are full or the aircraft is small. Your bag was compliant; the aeroplane ran out of room. Delta gate-checks at no charge when bin space is limited, and free of charge on Delta Connection aircraft of 50 seats or fewer. Airline’s own wordsDelta American valet-checks oversized carry-ons free on regional flights with limited overhead space. Airline’s own wordsAmerican Airlines Frontier gate-checks at no additional cost where there is no bin space. Airline’s own wordsFrontier Airlines
Paid — you did not buy the allowance, or the bag is genuinely oversized. On United, arriving at the gate with a full-size carry-on on a Basic Economy fare costs roughly $75: a $50 checked bag fee plus a $25 gate handling charge. ReportedNerdWallet Allegiant applies airport bag fees to oversized personal items and to oversized or excess carry-ons. Airline’s own wordsAllegiant
Neither Frontier nor Allegiant publishes a fixed gate price. Frontier points you at a dynamic bag price checker and says only that prices at the airport are higher; Allegiant says the same. Any site quoting you an exact Frontier gate carry-on fee is quoting a number the airline does not publish. Airline’s own wordsFrontier Airlines
The measurement everyone quotes — a United sizer at 23 × 15 × 10 against a published 22 × 14 × 9 — comes from one blogger in 2015, describing boxes United removed in 2020. The real and much better documented reason a “22-inch” bag fails a 22-inch sizer is that manufacturers measure the case and airlines measure the outside, wheels and handles included. That one is confirmed by the carriers themselves.
Full flights, boarding zone and particular hubs are repeated everywhere as enforcement triggers. They are operationally plausible — a full flight genuinely runs out of bin space. We could not attribute any of it to a single named source, so it stays off this page.
The best-known “they charged me and my bag fit” story was substantially rebutted: the videos omitted that the passengers were also carrying backpacks, jackets and in one case a second carry-on. The question at the gate is rarely whether one bag fits the box — it is whether everything you are carrying does. ReportedOne Mile at a Time
Several sites are promoting “new carry-on rules starting June 2026”. We found no airline statement, regulatory notice or reputable reporting behind it — only content farms citing each other. There is no industry-wide rule change.
The practical upshot: on the big carriers the risk has moved to check-in, and on the budget carriers it is at boarding and has historically been financially motivated. Check your bag against every airline before you rely on any of it.
Not all of them. United removed sizers from every gate in January 2020 and American did the same on 6 October 2025 — both kept them at check-in. Frontier still measures at boarding and has a separate smaller box for personal items. For the remaining US carriers there is no reliable public information either way, so we do not claim one.
At the budget carriers, yes. Frontier states that a personal item "must fit within the smaller sizer box" and checks it during boarding, and Allegiant charges specifically for oversized personal items. At the larger carriers it is mostly an eyeball test, and Delta publishes no personal item dimensions at all, so there is nothing to measure against.
Because at two of them they were paid per bag. A US Senate investigation published in November 2024 found Frontier and Spirit paid over $26 million in incentives to gate agents and other staff across 2022 and 2023, with Frontier personnel able to earn up to $10 for each bag a passenger was forced to check at the gate. Frontier publicly confirmed the programme exists.
No, and the distinction matters. If your bag is compliant and the bins are simply full, gate-checking is free — Delta, American and Frontier all state this. You pay when you did not buy the allowance in the first place, or when the bag is genuinely oversized. On United, bringing a full-size carry-on to the gate on a Basic Economy fare runs about $75.
This is widely repeated and poorly evidenced. The often-quoted measurement of a United sizer at 23 × 15 × 10 traces back to a single blogger measurement from 2015, describing equipment United removed in 2020. The far more common and better documented reason a "22-inch" bag fails a 22-inch sizer is that manufacturers measure the packing case while airlines measure the outside, wheels and handles included.
Manufacturers publish dimensions inconsistently, and a “20-inch” spinner is almost never 20 inches once you count the wheels. Where a brand states dimensions including wheels and handles, that’s the number we use. Where it only publishes the case, we say so on the card. Airlines measure the outside of your bag — wheels, handles, straps and all. Anything marked borderline is down to the gate agent, and remember that a soft bag squashes into a sizer while a hard shell won’t.
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Limits verified August 2026 against each carrier’s published policy. Airlines change these without notice — always confirm before you fly. Spirit Airlines ceased operations on 2 May 2026 and is no longer listed.
Airline Bag Size Checker v1.0.15 · last updated 2026-08-12