United and Southwest represent the two major models of US air travel in 2026: the global legacy carrier with Star Alliance reach, Polaris business class, and a Basic Economy fare that strips the carry-on, versus the domestic-focused carrier with bigger carry-on allowances, the Companion Pass, and a newly assigned seating system that still gives you more legroom than most competitors.
The comparison has shifted. Southwest now charges for checked bags and assigns seats, removing two of its most distinctive advantages. But the operational data still favors Southwest on reliability, and United’s domestic Basic Economy is the most restrictive of any US legacy carrier when it comes to bags. Those differences matter more than the converging fare structures.
Short version: Southwest is better for domestic-only travelers who value reliability, flexibility, and a larger carry-on. United is better for international travelers, Star Alliance loyalists, and anyone who needs premium cabin options beyond US borders.
What We Looked For
- Basic fare restrictions, because United and Southwest have the widest gap in what their cheapest ticket includes
- Carry-on and checked bag policies, with attention to the new fee landscape after Southwest’s policy change
- Reliability, measured by on-time rates and cancellations
- Route network, domestic point-to-point versus global hub-and-spoke
- Loyalty program value, including Companion Pass versus Star Alliance access
- Seat comfort, pitch and the extra-legroom upsell on each carrier
Which airline charges less for bags, United or Southwest?
Southwest includes a carry-on on every fare for free. United strips the carry-on on domestic Basic Economy, making Southwest cheaper for most bag-carrying travelers.
This is where the comparison gets sharpest, because United and Southwest handle the cheapest ticket completely differently.
United Basic Economy on domestic routes restricts you to a personal item only: 17x10x9 inches, no full carry-on. If you show up at the gate with a roller bag on a domestic Basic Economy ticket, United charges the checked bag fee plus a gate handling surcharge. MileagePlus Premier members and United co-brand credit card primary holders are exempt.
Southwest Basic (Wanna Get Away) includes a full carry-on at 24x16x10 inches plus a personal item on every fare. No restrictions, no upsell required, no credit card needed.
That is a significant gap. United’s Basic Economy is the most restrictive of the Big Three legacy carriers on carry-on bags (Delta and American both include the carry-on). For a traveler who does not hold United status or a credit card, this effectively makes the cheapest United fare $45 more expensive after adding a bag.
Checked bags. United charges $45 for the first checked bag ($50 at the airport) and $55 for the second ($60 at the airport). Southwest charges $45 for the first and $55 for the second on bookings from April 9, 2026 onward. Both airlines now charge the same prepaid online rate.
Carry-on dimensions. Southwest’s 24x16x10 is noticeably larger than United’s 22x14x9. Southwest also has a lower gate-check risk thanks to its consistent all-737 fleet, while United’s regional jets (CRJ-200, ERJ-145) cannot fit standard carry-ons.
For details on your specific bag, use our carry-on size checker or see our guide to avoiding checked bag fees.
- Winner for carry-on inclusion: Southwest (included on all fares vs stripped on United Basic Economy)
- Winner for carry-on size: Southwest (24x16x10 vs 22x14x9)
- Winner for checked bag fees: Tie ($45 first bag at both airlines)
- Winner for gate-check avoidance: Southwest (all-737 fleet, consistent bins)
Is United or Southwest more reliable?
Southwest is slightly more reliable, with a 79.92 percent on-time rate and the lowest cancellation rate of any major US carrier in 2025.
Both airlines are above average on reliability, but Southwest edges ahead.
Southwest’s 2025 on-time rate was 79.92 percent with a 0.82 percent cancellation rate, the lowest cancellation rate of any major US carrier. Southwest was ranked the most reliable US airline in 2025 by multiple evaluation systems, with the fewest cancellations and lowest rate of mishandled baggage.
United’s 2025 on-time rate was 78.84 percent, roughly one point behind Southwest. United’s cancellation rate was higher than Southwest’s but below the industry average. Both airlines are solidly reliable in 2026, unlike the American-versus-Southwest gap where the difference is stark.
- Winner for on-time arrivals: Southwest (79.92% vs 78.84%, marginal)
- Winner for cancellations: Southwest (0.82%, lowest in the industry)
- Winner for baggage handling: Southwest (0.4% mishandled, lowest among major carriers)
Does United or Southwest have more legroom?
Both offer 30 to 31 inches of standard pitch, with Southwest slightly more consistent across its all-737 fleet.
Standard economy pitch. Southwest offers 31 inches across its all-Boeing 737 fleet, reduced from 32 inches in 2026 to accommodate Extra Legroom rows. United’s narrowbody fleet offers 30 to 31 inches in standard economy.
Extra legroom. United’s Economy Plus provides 34 to 35 inches of pitch with priority boarding. Southwest’s new Extra Legroom rows offer similar additional space. Both are available as paid upgrades.
Wi-Fi. United offers free Wi-Fi for MileagePlus members on domestic flights (free to enroll). Southwest charges for Wi-Fi but offers free streaming entertainment through the app.
Entertainment. United has seatback screens on newer aircraft and streaming on others. Southwest has no seatback screens but provides free live TV and on-demand content via the app.
Assigned seating. Southwest transitioned to assigned seating on January 27, 2026. Passengers now choose Standard, Preferred, or Extra Legroom seats depending on fare level. United has always used assigned seating with Economy Plus as the paid upgrade tier.
- Winner for standard legroom: Tie (both 30-31”, Southwest slightly more consistent)
- Winner for Wi-Fi: United (free for MileagePlus members)
- Winner for entertainment: United (seatback screens on many aircraft)
Does United or Southwest fly to more destinations?
United flies to over 300 destinations on six continents. Southwest covers 117 domestic-focused airports with no transoceanic service.
United flies to over 300 destinations across six continents with major hubs at EWR, ORD, IAH, DEN, SFO, IAD, and LAX. Star Alliance membership connects to 26 partner airlines including Lufthansa, ANA, Singapore Airlines, and Air Canada.
Southwest flies to approximately 117 airports in 11 countries, focused on the contiguous United States, Hawaii, Mexico, Central America, and the Caribbean. No widebody aircraft, no transoceanic flights, no alliance partnerships (though individual codeshares exist).
For domestic flights, both airlines cover most major and mid-size markets. Southwest’s point-to-point model often avoids connections that United’s hub-and-spoke system requires. For international travel, United is the only choice.
- Winner for international: United (300+ destinations, 6 continents, Star Alliance)
- Winner for domestic point-to-point: Southwest (fewer connections on popular routes)
Is MileagePlus or Rapid Rewards the better loyalty program?
MileagePlus is better for international travelers with Star Alliance access. Rapid Rewards is better for families thanks to the Companion Pass.
MileagePlus earns miles based on fare price and partner spending. Miles are worth approximately 1.5 cents each on average, with strong redemption rates on Star Alliance partners. Elite tiers (Silver, Gold, Platinum, 1K) unlock free upgrades, economy Plus, and United Club access. Premier 1K members get the broadest upgrade priority and a complimentary United Club membership.
Rapid Rewards earns points based on fare price. Points average 1.4 cents each, slightly below MileagePlus. The Companion Pass (135,000 qualifying points or 100 flights in a calendar year) lets a designated companion fly free on every flight for up to two years. No blackout dates on award flights. Free flight changes and cancellations on most fares.
- Winner for international redemptions: MileagePlus (Star Alliance, 26 partners)
- Winner for families: Rapid Rewards (Companion Pass)
- Winner for flexibility: Rapid Rewards (free changes, no blackout dates)
- Winner for upgrade path: MileagePlus (complimentary upgrades with elite status)
Who Should Pick United
- You fly internationally and need a carrier with global reach and premium cabins
- Your home airport is a United hub (EWR, ORD, IAH, DEN, SFO)
- You hold MileagePlus status or a United credit card that waives the Basic Economy bag restriction
- You value Star Alliance partner redemptions
- You want United Club or Polaris lounge access
- You fly enough to earn Premier status and complimentary upgrades
Who Should Pick Southwest
- You fly mostly domestic and want a carry-on included on every fare without needing status or a credit card
- You travel as a couple or family and can earn the Companion Pass
- You want the flexibility to change or cancel flights without fees
- You carry a larger bag that fits Southwest’s 24x16x10 but not United’s 22x14x9
- You want the most reliable US carrier by cancellation rate
- Your travel schedule changes often and you value rebooking without penalty
The Bottom Line
United’s domestic Basic Economy is the tightest in the industry. No carry-on on the cheapest fare is a meaningful restriction for travelers who do not hold status or a co-brand credit card. Southwest includes a larger carry-on on every fare, and that alone can be worth $45 per flight in avoided bag fees.
Where United wins is everywhere outside the US border. Star Alliance access, Polaris business class, and 300+ global destinations are capabilities Southwest simply does not have and is not building toward. If you fly internationally even a few times a year, MileagePlus earns and redeems in ways Rapid Rewards cannot match.
For the domestic-only traveler, Southwest’s combination of reliability, carry-on generosity, Companion Pass, and flexibility makes it the better default in 2026. For the traveler who crosses an ocean, United is the clear pick.