Frontier vs Southwest: Which Budget Airline Actually Costs Less After Fees? (2026)

The verdict

For travellers packing only a personal item (under-seat bag) with no seat preference, Frontier is slightly cheaper than Southwest — by $10–$30 on average. For everyone else — anyone needing a carry-on, wanting to pick a seat, or valuing the ability to cancel — Southwest's higher base fare results in equal or lower total cost after fees. This holds for most domestic routes where both carriers compete. The exceptions are Frontier's FRONTIER Miles All-You-Can-Fly pass ($599/year) for ultra-frequent budget travellers, and specific routes where Frontier drops base fares below $29 as loss leaders — genuine deals that beat any Southwest equivalent.

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Key reasoning

Frontier operates a pure unbundled model — you pay for every component separately. The base fare covers a seat and a personal item only. A carry-on bag costs $45–$99 (depending on when you add it), a checked bag costs $45–$99, and a seat assignment costs $15–$50. For a traveller who adds just a carry-on, the total jumps by $45–$99 each way.

Southwest's model includes carry-on bags and one personal item at no extra cost. After Southwest's 2026 policy changes (eliminating no-fee changes and free checked bags for most passengers), its advantage narrowed — but carry-on bags remain free, which is the key differentiator for most travellers.

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Supporting facts / breakdown

Fee Category	Frontier (typical)	Southwest (typical)
Base fare (example route)	$49	$89
Personal item (under seat)	Free	Free
Carry-on bag (overhead)	$45–$99	Free
1st checked bag	$45–$99	$35 (free with SW card)
Seat assignment	$15–$50	Free (open seating)
Flight change fee	$99	$0 credit retained
Total (personal item only)	$49	$89
Total (carry-on + seat)	$109–$198	$89
Total (carry-on + checked + seat)	$154–$297	$124

The numbers show that Frontier's cost advantage disappears the moment you add a carry-on bag — at that point, Southwest's higher base fare results in equal or lower all-in spending.

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How to apply this

Use the Frontier Fee Stack Test: start with Frontier's base fare and add the fees for every service you'll actually use. If the total exceeds Southwest's base fare for the same route, book Southwest. If Frontier's all-in cost is still lower, book Frontier.

The test rarely favours Frontier for travellers with bags. It consistently favours Frontier for true minimalists (personal item only, no seat preference, no risk of itinerary change).

Traveller Type	Best Choice	Reason
Personal item only, flexible, low change risk	Frontier	Saves $30–$50 vs Southwest base fare
Carry-on bag + seat preference	Southwest	Frontier adds $60–$150 in fees
Family of 4, checked bags	Southwest	SW carry-on free; Frontier adds $360–$800 in bag fees
Traveller with uncertain itinerary	Southwest	Frontier's $99 change fee erases any fare saving
Frequent budget flyer (20+ trips/year)	Frontier GoWild pass	$599/year all-you-can-fly is unbeatable at volume

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What this actually means

Booking Southwest through ShopBack earns cashback on the base fare — on a $158 all-in Southwest round-trip, that's $8–$16 back, further widening the advantage over Frontier's $208 all-in cost after carry-on fees.

In practice, this means most travellers should book Southwest unless they are genuinely travelling with a personal item only and have a fixed itinerary with no possibility of change. The typical American traveller brings at least a carry-on bag — and that single add-on is enough to make Southwest cheaper.

A concrete example: two friends flying from Denver to Las Vegas. Frontier base fare: $39. Southwest base fare: $79. Frontier advantage: $40. Both travellers have a carry-on. Frontier overhead carry-on: $65 each way x 2 = $130 round-trip. Southwest carry-on: free. All-in: Frontier $208 vs Southwest $158. Southwest is $50 cheaper, despite the lower Frontier base fare.

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When this does NOT apply

• Frontier's sub-$29 loss-leader sales: Frontier periodically runs route-specific sales at $19–$29 base fares. At this price, even adding a carry-on fee keeps the total below Southwest's fare. Monitor Frontier's email list or deal sites for these.
• Frontier GoWild All-You-Can-Fly Pass ($599/year): For travellers flying 20+ times annually with flexibility on timing, this pass makes Frontier the clear winner — no other US airline offers an all-inclusive unlimited flying model.
• Routes without Southwest service: Frontier operates some routes that Southwest doesn't (smaller markets, some Florida routes). On those, Frontier is the only budget option.
• Travellers with the Frontier credit card: The Frontier World Mastercard ($89/year) includes free carry-on bag + first checked bag + seat selection — eliminating the main fee disadvantages and making Frontier competitive even for bag-carrying travellers.
• One-way trips with minimal luggage: The Frontier base fare advantage is most pronounced on one-way bookings where the fee asymmetry doesn't compound over a round-trip.

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Frequently asked questions

Is Spirit or Frontier cheaper than Southwest?

Both Spirit and Frontier have lower base fares, but their fee structures are nearly identical — carry-on bags, seat assignments, and change fees add up quickly. For most travellers with any luggage, Southwest's all-in pricing is competitive or cheaper.

Does Frontier have better routes than Southwest?

Frontier has a somewhat different route network — stronger in Denver hub routes and some secondary markets. Southwest dominates in Texas, the Southwest, and point-to-point leisure routes. Neither is strictly "better" — coverage depends on your origin city.

Is Frontier Airlines reliable?

Frontier's on-time performance and customer satisfaction scores are generally lower than Southwest's. Frontier ranks near the bottom of major US carriers for both completion rates and customer complaints — a real operational risk for tight itineraries.

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Key takeaways

• If you're packing a personal item only and have a fixed itinerary, Frontier can save $30–$50 over Southwest
• If you need a carry-on bag, Southwest is equal or cheaper than Frontier all-in
• If your itinerary might change, Southwest's retained travel credit beats Frontier's $99 change fee every time
• If you fly 20+ times a year and can be flexible, look at Frontier's GoWild pass — nothing else competes at that volume
• If you have the Frontier credit card, the fee advantage narrows significantly and Frontier becomes more competitive
• Book Southwest through ShopBack — $8–$16 cashback on a $158 all-in fare further widens the gap over Frontier's fee-laden total, no promo codes needed

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Disclaimer

The views and recommendations expressed in this article are those of the author.

Prices, rates, promotions, and availability are subject to change. Please verify details directly with the relevant providers before making any decisions.

This article is intended for general informational purposes only and should not be considered professional, financial, or travel advice.