Carry On fees by airline
Last verified: 2026-08-23Carry-on rules are really enforcement rules. The published dimensions matter, but the real money is won or lost on whether the airline monetizes cabin access aggressively.
Best for: deciding whether to buy cabin space, pack smaller, or change airlines before reaching the gate.
Quick check: Treat bag shape as part of the cost decision. Soft, compressible bags often outperform rigid rollers even when the claimed dimensions look similar.
Common way to avoid the fee: On some airlines, buying the right seat or bundle is actually a cheaper way to buy cabin-bag access than paying for the bag as a standalone add-on.
What to watch: Check whether the fare includes a full cabin bag, only a personal item, or a paid upgrade path that changes the all-in fare.
Carry-on decisions get easier when you pair this page with the carry-on strictness guide, then check Spirit, Frontier, and Ryanair before using Sizer rules to test whether your bag survives real enforcement.
Published fees on this page: 101
Decision tools
Choose the next step for this fee
Carry-on sizer comparison
Compare a bag's outside dimensions against published carry-on and personal-item rules.
Carry-on strictness guide
Decide whether the real issue is published dimensions, fare restrictions, or gate enforcement culture.
Basic Economy decision tool
Check whether the cheapest fare is risky because it restricts carry-on access, seats, or flexibility.
Common situations
This is really an enforcement page
Carry-on pricing matters because airlines differ widely in whether they treat the bag as included, optional, or a paid add-on.
Bag shape beats bag marketing
A soft bag that actually compresses is often more valuable than a roller marketed with optimistic dimensions.
Europe LCCs and US ULCCs are the key comparison set
Ryanair, easyJet, Spirit, and Frontier show why cabin-bag access needs to be priced before the fare is compared.
Airline pages to compare next
Spirit is where the personal-item game determines whether the fare stays cheap.
Frontier is useful because timing and bundle choice change the outcome fast.
Published fees and sources
| Airline | Amount | Applies to | Region / route | Timing | Conditions | Source | Last verified | Next step |
|---|---|---|---|---|---|---|---|---|
| Aer Lingus (EI) | 0 EUR | Saver fares | All routes | per flight | Small personal item is included for everyone; 10 kg bag handling depends on route and fare | Source | 2026-08-23 | |
| Aer Lingus (EI) | From 9.99 EUR | Optional add-on / bundled fares | All routes | at booking / manage booking | 10 kg bag onboard is paid or included; Saver gate presentation without entitlement triggers a hold fee | Source | 2026-08-23 | |
| Aeroméxico (AM) | 0 USD | All fares | All routes | per flight | Carry-on depends on cabin and fare; Basic and Light use separate paid extra-weight products | Source | 2026-08-23 | |
| Air Astana (KC) | 0 USD | All fares | All routes | per flight | Carry-on is included; cabin and fare determine the weight limit, and infant items may count separately when allowed | Source | 2026-08-23 | |
| Air Canada (AC) | 0 CAD | All fares | All routes | per flight | One standard carry-on and one personal item are included; aircraft, fare enforcement, and gate checks can affect handling | Source | 2026-08-23 | |
| Air China (CA) | 0 CNY | All fares | All routes (Air China–operated flights) | per flight | Economy Class: 1 cabin bag up to 8 kg; Business/First Class have higher allowances; size limits apply | Source | 2026-08-23 | |
| Air India (AI) | 0 INR | All fares | All routes (Air India-operated flights) | per flight | 1 cabin bag plus 1 small personal item. Economy/Premium Economy: 7 kg; Business/First: 10 kg. | Source | 2026-08-23 | |
| Air New Zealand (NZ) | 0 NZD | All fares | All routes (Air New Zealand-operated flights) | per flight | Economy carry-on is 7 kg plus personal item; status and higher cabins can change allowance | Source | 2026-08-23 | |
| AIX Connect / Air India Express (IX) | 0 INR | All fares | All routes | per flight | Air India Express allows 7 kg total cabin baggage; Xtra Carry-On can raise this to 12 kg where available | Source | 2026-08-23 | |
| All Nippon Airways (NH) | 0 JPY | All fares | All routes | per flight | Carry-on allowance is 10 kg total including personal item, with standard item-size limits | Source | 2026-08-23 | |
| Asiana Airlines (OZ) | 0 KRW | All fares | All routes (Asiana-operated flights) | per flight | Economy Class: 1 cabin bag up to 10 kg; Business/First Class have higher allowances; size limits apply | Source | 2026-08-23 | |
| Avianca (AV) | 0 USD | All fares | All routes (Avianca-operated flights) | per flight | Carry-on depends on fare family; international Light fares now include a 10 kg carry-on, while domestic Basic starts with a personal item | Source | 2026-08-23 | |
| Avianca (AV) | Depends on route and timing USD | Basic fare | All routes | at booking / manage booking | Paid carry-on applies mainly to Basic-style gaps; price depends on route, channel, timing, and peak season | Source | 2026-08-23 | |
| Batik Air (ID) | 0 IDR | All fares | All routes (Batik Air–operated flights) | per flight | Economy Class: 1 cabin bag up to 7 kg plus 1 personal item; size limits apply | Source | 2026-08-23 | |
| Cathay Pacific (CX) | 0 HKD | All fares | All routes | per flight | Carry-on is cabin-based; Economy/Premium Economy get one 7 kg piece, while Business/First get two | Source | 2026-08-23 | |
| Cebu Pacific (5J) | 0 USD | All fares | All routes | per flight | Hand-carry is included up to 7 kg total; size limits apply and checked bags depend on fare bundle/add-ons | Source | 2026-08-23 | |
| China Airlines (CI) | 0 TWD | All fares | All routes (China Airlines–operated flights) | per flight | Economy includes 1 cabin bag up to 7 kg plus 1 personal item; premium cabins have higher allowances. | Source | 2026-08-23 | |
| China Eastern Airlines (MU) | 0 CNY | All fares | All routes (China Eastern–operated flights) | per flight | Economy Class: 1 cabin bag up to 8 kg; Business/First have higher allowances; size limits apply | Source | 2026-08-23 | |
| China Southern Airlines (CZ) | 0 CNY | All fares | All routes (China Southern–operated flights) | per flight | Economy Class: 1 cabin bag up to 8 kg; Business and First Class have higher allowances; size limits apply | Source | 2026-08-23 | |
| Copa Airlines (CM) | 0 USD | All fares | All routes (Copa-operated flights) | per flight | Carry-on depends on fare family and route; size and weight limits still apply at the gate | Source | 2026-08-23 | |
| easyJet (U2) | 0 GBP | All fares | All routes | per flight | Every fare includes one small underseat bag up to 45 x 36 x 20 cm and 15 kg, if the traveler can lift it | Source | 2026-08-23 | |
| easyJet (U2) | From 5.99 GBP | Optional add-on / seat bundle | All routes | at booking / manage booking | Large cabin bag price varies by route, flight, timing, availability, fare, seat, or easyJet Plus status | Source | 2026-08-23 | |
| easyJet (U2) | 48 GBP | Cabin bags larger than the free small-bag allowance | All routes | boarding gate | Airport/gate bag fee for non-purchased or oversized cabin bags placed in the hold | Source | 2026-08-23 | |
| EgyptAir (MS) | 0 USD | All fares | All routes | per flight | Cabin baggage depends on cabin and route; international tables publish class-specific carry-on limits | Source | 2026-08-23 | |
| Emirates (EK) | 0 AED | All fares | All routes | per flight | Economy: 1 carry-on up to 7 kg. Premium Economy: 1 up to 10 kg. Business/First: 2 up to 7 kg each. | Source | 2026-08-23 | |
| Ethiopian Airlines (ET) | 0 USD | All fares | All routes (Ethiopian Airlines–operated flights) | per flight | Economy includes 1 cabin bag up to 7 kg plus a personal item; Business has higher allowance. | Source | 2026-08-23 | |
| Etihad Airways (EY) | 0 USD | All fares | All routes (Etihad-operated flights) | per flight | Cabin allowance depends on fare, cabin, ticket date, and route; published fare tables changed in 2026. | Source | 2026-08-23 | |
| EVA Air (BR) | 0 TWD | All fares | All routes (EVA Air-operated flights) | per flight | Premium Economy/Economy: 1 carry-on up to 7 kg. Business cabins: 2 carry-ons up to 7 kg each. | Source | 2026-08-23 | |
| Garuda Indonesia (GA) | 0 IDR | All fares | All routes (Garuda Indonesia–operated flights) | per flight | Economy Class: 1 cabin bag up to 7 kg plus 1 personal item; Business and First Class have higher allowances; size limits apply | Source | 2026-08-23 | |
| Gulf Air (GF) | 0 USD | All fares | All routes | per flight | Carry-on allowance included; weight and size limits depend on cabin class | Source | 2026-08-23 | |
| Hainan Airlines (HU) | 0 CNY | All fares | All routes (Hainan Airlines–operated flights) | per flight | Economy Class: 1 cabin bag up to 10 kg; Business Class has higher allowance; size limits apply | Source | 2026-08-23 | |
| Hong Kong Airlines (HX) | 0 HKD | All fares | All routes (Hong Kong Airlines–operated flights) | per flight | Economy Class: 1 cabin bag up to 7 kg plus small personal effects; Business Class allowance higher; size limits apply | Source | 2026-08-23 | |
| Iberia (IB) | 0 EUR | All fares | All routes | per flight | Cabin bag and personal item are included; weight and piece rules vary by cabin and operating carrier | Source | 2026-08-23 | |
| Iberia Express (I2) | 0 EUR | All fares | All routes | per flight | Cabin bag and personal item are included; size/weight rules are fare and cabin dependent | Source | 2026-08-23 | |
| IndiGo (6E) | 0 INR | All fares | Domestic India / International varies | per flight | Domestic flights: 1 cabin bag up to 7 kg plus 1 personal item; International allowances vary by route; size limits apply | Source | 2026-08-23 | |
| Japan Airlines (JL) | 0 JPY | All fares | All routes | per flight | Carry-on is included up to 10 kg total including personal item; size limits apply | Source | 2026-08-23 | |
| Jet2.com (LS) | 0 GBP | All fares | All routes | per flight | Small under-seat bag is included; it is checked at airport and boarding gates | Source | 2026-08-23 | |
| Jet2.com (LS) | 0 GBP | All fares | All routes | per flight | One 10 kg cabin bag is included; extra or oversize hand baggage is charged at airport/gate | Source | 2026-08-23 | |
| Jetstar (JQ) | 0 AUD | All fares | All routes | per flight | Base fares include limited cabin baggage; extra carry-on weight or overhead access must be bought where available | Source | 2026-08-23 | |
| Jetstar Japan (GK) | 0 JPY | All fares | All routes | per flight | Standard carry-on is 7 kg total across two items; extra carry-on is limited and route-dependent | Source | 2026-08-23 | |
| Kenya Airways (KQ) | 0 USD | All fares | All routes | per flight | Carry-on baggage included; allowance depends on cabin class; size and weight limits apply | Source | 2026-08-23 | |
| KLM Royal Dutch Airlines (KL) | 0 EUR | All fares | All routes (KLM-operated flights) | per flight | Basic includes only a small underseat bag. Light/Standard/Flex include small bag plus hand baggage, 12 kg combined. | Source | 2026-08-23 | |
| KLM Royal Dutch Airlines (KL) | Shown during booking / My Trip EUR | Economy Light | All routes (KLM-operated flights) | at booking / manage booking | Basic fares can buy 1 hand-baggage piece in My Trip up to 4 hours before departure. | Source | 2026-08-23 | |
| Korean Air (KE) | 0 KRW | All fares | All routes | per flight | Carry-on is cabin-based: Economy gets one 10 kg piece; Prestige/First get two 10 kg pieces | Source | 2026-08-23 | |
| LATAM Airlines (LA) | 0 USD | All fares | All routes | per flight | Basic can be personal-item-only on some domestic South America routes; Light adds a 12 kg cabin bag. | Source | 2026-08-23 | |
| Malaysia Airlines (MH) | 0 MYR | All fares | All routes (Malaysia Airlines–operated flights) | per flight | Economy includes 1 cabin bag up to 7 kg plus 1 personal item; premium cabins have higher allowances. | Source | 2026-08-23 | |
| Norwegian (DY) | 0 EUR | LowFare | All routes | per flight | LowFare includes only an under-seat item; overhead cabin baggage is a fare or paid-benefit issue | Source | 2026-08-23 | |
| Norwegian (DY) | 0 EUR | LowFare+, Flex | All routes | per flight | LowFare+ and Flex include overhead cabin baggage; Reward benefits can also add it when active | Source | 2026-08-23 | |
| Oman Air (WY) | 0 USD | All fares | All routes | per flight | Carry-on baggage included; Economy Class allowance up to 7 kg; Business and First Class allowances higher; size limits apply | Source | 2026-08-23 | |
| Philippine Airlines (PR) | 0 PHP | All fares | All routes (Philippine Airlines–operated flights) | per flight | Economy Class: 1 cabin bag up to 7 kg plus 1 personal item; Premium Economy and Business Class have higher allowances; size limits apply | Source | 2026-08-23 | |
| Qantas Airways (QF) | 0 AUD | All passengers | All routes | per flight | Carry-on is included, but size, weight, and piece limits depend on route, cabin, and aircraft. | Source | 2026-08-23 | |
| Qatar Airways (QR) | 0 QAR | All fares | All routes | per flight | Economy: 1 carry-on up to 7 kg. Business/First: 2 carry-ons with a combined 15 kg allowance. | Source | 2026-08-23 | |
| Royal Air Maroc (AT) | 0 USD | All fares | All routes | per flight | Carry-on allowance depends on cabin and route; standard size and weight limits apply | Source | 2026-08-23 | |
| Ryanair (FR) | 0 EUR | Basic fare | All routes | per flight | All fares include one small underseat bag only; larger cabin baggage requires Priority or checked-bag purchase | Source | 2026-08-23 | |
| Ryanair (FR) | From 6 to 36 EUR | Optional add-on | All routes | at booking / manage booking | Priority & 2 Cabin Bags adds a 10 kg overhead bag; price varies by route, date, availability, and timing | Source | 2026-08-23 | |
| Ryanair (FR) | From 20 to 60 EUR/GBP | Optional add-on | All routes | post-booking / airport | Post-booking/airport Priority or gate handling costs more and depends on route and travel date | Source | 2026-08-23 | |
| Saudia (Saudi Arabian Airlines) (SV) | 0 USD | All fares | All routes (Saudia-operated flights) | per flight | Guest cabin bag is 7 kg; First/Business hand bag is 12 kg plus briefcase up to 9 kg, with route notes. | Source | 2026-08-23 | |
| Singapore Airlines (SQ) | 0 SGD | All fares | All routes | per flight | Economy/Premium Economy: 1 cabin bag up to 7 kg. Business/First/Suites: 2 bags up to 7 kg each. | Source | 2026-08-23 | |
| South African Airways (SA) | 0 USD | All fares | All routes | per flight | Economy includes one 8 kg cabin bag plus personal item; Business includes two 8 kg cabin bags plus personal item | Source | 2026-08-23 | |
| SpiceJet (SG) | 0 INR | All fares | All routes | per flight | Standard cabin baggage is 7 kg; paid Carry More On-board can add up to 5 kg where available | Source | 2026-08-23 | |
| Spring Airlines (9C) | 0 CNY | All fares | All routes | per flight | Carry-on weight and dimensions depend on ticket class; stricter low-fare limits can apply | Source | 2026-08-23 | |
| SriLankan Airlines (UL) | 0 USD | All fares | All routes (SriLankan Airlines–operated flights) | per flight | Economy Class: 1 cabin bag up to 7 kg; Business Class allowance higher; size limits apply | Source | 2026-08-23 | |
| TAP Air Portugal (TP) | 0 EUR | All fares | All routes | per flight | Hand baggage depends on fare, cabin, route, and size/weight limits; enforcement is at airport | Source | 2026-08-23 | |
| Thai Airways (TG) | 0 THB | All fares | All routes (Thai Airways–operated flights) | per flight | Economy Class: 1 cabin bag up to 7 kg; Business and First Class have higher allowances; size limits apply | Source | 2026-08-23 | |
| Turkish Airlines (TK) | 0 USD | All fares | All routes | per flight | Carry-on is cabin-based: Economy gets one 8 kg piece; Business gets two 8 kg pieces | Source | 2026-08-23 | |
| VietJet Air (VJ) | 0 USD | All fares | All routes | per flight | Eco/Deluxe include 7 kg carry-on; SkyBoss/Business can include more; priority carry-on is a paid route-priced add-on | Source | 2026-08-23 | |
| Vietnam Airlines (VN) | 0 VND | All fares | All routes (Vietnam Airlines–operated flights) | per flight | Economy/Premium Economy carry-on is 10-12 kg by route; Business is 18 kg; ATR72 flights are 7 kg. | Source | 2026-08-23 | |
| Virgin Australia (VA) | 0 AUD | All fares | All routes | per flight | Economy includes one 8 kg cabin bag plus personal item; Business, Economy X, and eligible Velocity tiers may get 14 kg combined | Source | 2026-08-23 | |
| Vistara (UK) | 0 INR | Historical Vistara / current Air India-managed AI 2XXX context | Former Vistara network | archival; current travel uses Air India policy | Archival Vistara reference only; current former-Vistara flights use Air India carry-on rules | Source | 2026-08-23 | |
| Viva Aerobus (VB) | 0 USD | All fares | All routes | per flight | All fares include a personal item; Light/Extra include 10 kg carry-on and Smart can raise cabin allowance to 15 kg | Source | 2026-08-23 | |
| Volaris (Y4) | 0 USD | All fares | All routes | per flight | Zero and Basic include only a personal item; Plus includes carry-on, and paid add-ons or INVEX benefits can add it | Source | 2026-08-23 | |
| Vueling (VY) | 0 EUR | Basic fare | All routes | per flight | Every fare includes one underseat cabin bag; large cabin bag access depends on fare, paid add-on, infant, or availability | Source | 2026-08-23 | |
| Vueling (VY) | From EUR 10 to 59 online; higher at airport/gate EUR | Optional add-on / bundled fares | All routes | at booking / manage booking | Overhead cabin bag price depends on route, date, bundle, seat choice, and whether bought online or at airport | Source | 2026-08-23 | |
| WestJet (WS) | 0 CAD | All fares | All routes | per flight | UltraBasic is personal-item only except Europe/Asia or Extended Comfort; other fares include carry-on plus personal item | Source | 2026-08-23 | |
| Wizz Air (W6) | 0 EUR | Basic fare | All routes | per flight | Basic fare includes one underseat bag; overhead trolley access requires WIZZ Priority or an eligible bundle | Source | 2026-08-23 | |
| Wizz Air (W6) | EUR 10-60 online; EUR 65-75 airport EUR | Optional add-on | All routes | at booking / manage booking | WIZZ Priority adds a 10 kg trolley bag; price changes by route, season, availability, and purchase timing | Source | 2026-08-23 | |
| XiamenAir (MF) | 0 CNY | All fares | All routes (XiamenAir-operated flights) | per flight | Economy Class: 1 cabin bag up to 7 kg; Business Class allowance higher; size limits apply | Source | 2026-08-23 | |
| ZIPAIR Tokyo (ZG) | 0 JPY | All fares | All routes | per flight | Fare includes 7 kg carry-on total; extra carry-on weight/package can raise allowance where available | Source | 2026-08-23 | |
| Air France (AF) | 0 EUR | All fares | All routes (Air France-operated flights) | per flight | Cabin allowance depends on fare and cabin; Basic may include only a small underseat bag unless hand baggage option is added | Source | 2026-08-22 | |
| AirAsia (AK) | 0 USD | All fares | All routes | per flight | Allowance is 2 cabin pieces totaling 7 kg; Low Fare includes cabin baggage but not checked baggage | Source | 2026-08-22 | |
| Alaska Airlines (AS) | 0 USD | All fares (including Saver) | All routes | per flight | One standard carry-on plus one smaller personal item are included, including Saver, subject to aircraft space | Source | 2026-08-22 | |
| American Airlines (AA) | 0 USD | All fares | All routes | per flight | One carry-on and one personal item are included, including Basic Economy; regional aircraft may require gate-checking | Source | 2026-08-22 | |
| British Airways (BA) | 0 GBP | All fares | All routes | per flight | One cabin bag and one handbag/personal item are included; cabin bag may be placed in hold if space is limited | Source | 2026-08-22 | |
| Delta Air Lines (DL) | 0 USD | All fares | All routes | per flight | One carry-on and one personal item are included; Basic/Main Basic keeps normal carry-on access | Source | 2026-08-22 | |
| flydubai (FZ) | 0 USD | All fares | All routes | per flight | Economy includes 1 cabin bag up to 7 kg; Business includes 2 pieces totaling 14 kg with 7 kg per piece | Source | 2026-08-22 | |
| flydubai (FZ) | 55 USD | Oversized or overweight hand baggage | All routes | at boarding gate | Gate fee applies per item when hand baggage exceeds size or weight; local taxes may apply | Source | 2026-08-22 | |
| Frontier Airlines (F9) | 0 USD | All fares | All routes | per flight | Every fare includes one personal item; boarding checks can trigger charges if it exceeds 8 x 18 x 14 in | Source | 2026-08-22 | |
| Frontier Airlines (F9) | Bag Price Checker / booking flow USD | All fares | All routes | per flight | Carry-on price depends on route, date, and purchase timing; airport and gate purchase can cost more | Source | 2026-08-22 | |
| JetBlue (B6) | 0 USD | All fares | All routes | per flight | One carry-on and one personal item are included on all fares, including Blue Basic since Sept. 6, 2024 | Source | 2026-08-22 | |
| Lufthansa (LH) | 0 EUR | Economy / Premium Economy | All routes (rules may vary by origin) | per flight | Economy and Premium Economy include 1 carry-on item up to 56 x 36 x 23 cm and 7 kg, plus a small personal item. | Source | 2026-08-22 | |
| Lufthansa (LH) | 0 EUR | Business / First | All routes (rules may vary by origin) | per flight | Business and First include 2 carry-on items, each up to 56 x 36 x 23 cm and 7 kg, plus a small personal item. | Source | 2026-08-22 | |
| Scoot (TR) | 0 USD | All fares | All routes | per flight | Economy allows 2 cabin pieces up to 10 kg total; ScootPlus allows 2 pieces up to 15 kg total | Source | 2026-08-22 | |
| Southwest Airlines (WN) | 0 USD | All fares | All routes | per flight | Carryon plus personal item remain free across fare types; checked-bag benefits now vary by fare/status/card/military path | Source | 2026-08-22 | |
| Spirit Airlines (NK) | Depends on purchase timing USD | Value | All routes | per flight | Archival: Value carry-on pricing varied by route and timing before Spirit's May 2026 wind-down | Source | 2026-08-22 | |
| United Airlines (UA) | 0 USD | Economy and higher fares | Most United-operated routes | per flight | Personal item plus standard carry-on included on Economy and higher fares; aircraft space can still affect handling | Source | 2026-08-22 | |
| United Airlines (UA) | Personal item only USD | Basic Economy | Route and exemption dependent | per flight | Basic Economy is usually personal-item only; full carry-on exceptions depend on route, Premier status, or eligible card | Source | 2026-08-22 | |
| Spirit Airlines (NK) | 0 USD | Value / Premium Economy / Spirit First | All routes | per flight | Archival: One personal item included; must fit completely under the seat in front of you | Source | 2026-05-06 | |
| Spirit Airlines (NK) | 0 USD | Premium Economy | All routes | per flight | Archival: Carry-on bag included with Premium Economy travel option | Source | 2026-05-06 | |
| Spirit Airlines (NK) | 0 USD | Spirit First | All routes | per flight | Archival: Carry-on bag included with Spirit First travel option | Source | 2026-05-06 | |
| Air France (AF) | Shown during booking EUR | Basic fare (Economy) | All routes (Air France-operated flights) | at booking / manage booking | Basic fare Hand Baggage option; price shown during purchase or in My Bookings; purchasable up to 4 hours before departure. | Source | 2025-12-24 | |
| Jetstar Asia (3K) | 0 SGD | All fares | All routes | per flight | Carry-on allowance varies by fare; Starter includes 7 kg, while higher fares may allow more | Source | 2025-12-24 |
The Next step column moves from the fee row into the relevant calculator or airline-specific guide. For checked baggage, Price bags estimates the cash bill and Card break-even tests whether repeat first-bag fees can justify an eligible card on bag savings alone. For carry-on and seat rows, the next question is usually whether the fare restriction changes the real trip cost.
Carry-on decisions get easier when you pair this page with the carry-on strictness guide, then check Spirit, Frontier, and Ryanair before using Sizer rules to test whether your bag survives real enforcement.
Related references
After checking the carry-on rows, the most useful next step is usually the airline-specific page or the enforcement guide that shows how strict the rule is in practice.
Compare the bag's actual dimensions before relying on an overhead-bin plan.
Best when the question is not just the size limit, but whether the airline is likely to enforce it.
Best when the cheapest fare may restrict carry-on access or make a checked bag more likely.
Price the checked-bag fallback when the carry-on plan is too risky.
Carry-on restrictions are one of the main ways cheap fares stop being cheap.