# Southwest post-Labor Day fares: verify LAX round-trips under $150

Riley Quinn · October 14, 2026

> Southwest post-Labor Day fares: find LAX round-trips under $150, DEN–PHX from $177, and December as the cheapest month to fly this route now.

| Takeaway | Detail |
| --- | --- |
| Southwest round-trips between Denver and Phoenix have been listed starting at $177 | Expedia lists Southwest DEN–PHX roundtrip fares from $177, with one-way from $89 or $43 depending on the listing |
| December is the cheapest month for Southwest on the DEN–PHX route | KAYAK reports December return tickets average $273, making it the cheapest month versus more expensive months on the route |
| Frontier undercuts Southwest on DEN–PHX pricing | Expedia shows Frontier at $116 versus Southwest at $177 as the cheapest carriers on the route |
| Every fare must be verified in the live booking flow before committing | Reader rule: confirm the complete option and compare like-for-like totals and terms; prices were available within the past 7 days and availability changes |

 This guide explains how Southwest's post-Labor Day fare sale prices LAX round-trips to Denver and Phoenix, using the most recent published fare data as the benchmark.

 It does not name specific discounted dates — no such date list appears in the underlying fare data — and instead walks through the verify-before-you-commit checks needed to find any dates that price under $150 in the live booking flow and to compare like-for-like totals and terms.

## How It Works

 Southwest's post-Labor Day fare sale works through its own booking flow, not through third-party aggregators, so the mechanism you need to understand is simple: the advertised sale price is a base fare that only becomes real when you run your specific LAX-to-Denver or LAX-to-Phoenix dates through Southwest's Low Fare Calendar and then the booking screen. The calendar shows the lowest available fare per day for your round-trip pair; the booking screen then shows the full total with taxes and fees before you pay. Verify at both steps — a fare that appears in the calendar can disappear between the calendar view and the payment screen, because availability is live and other travelers are booking the same inventory.

 A few key terms will keep you oriented. "Wanna Get Away" is Southwest's lowest fare class and the one sale pricing typically applies to; higher fare classes price higher and carry different terms. "One-way" and "round-trip" are not interchangeable units — Expedia's listings for the Denver–Phoenix market, for example, show fares starting at $43 one-way and $86 round-trip, and Southwest fares on that route have been listed from $89 one-way and $177 round-trip. Never compare a one-way figure against a round-trip figure; divide or double only when the units match. "Base fare" is the pre-tax number, while the booking screen total includes taxes and mandatory fees — compare like-for-like totals, not headline numbers.

 Two Southwest-specific terms matter for the total. First, checked bags: Southwest includes two free checked bags per passenger, a policy that other sources value at $140 or more per round-trip versus carriers that charge bag fees — so a Southwest total that looks slightly higher on the fare line can be lower once bags are counted. Second, the "return" average: Kayak reports that December is the cheapest month for Southwest flights from Denver to Phoenix, with return tickets averaging $273, which tells you seasonal averages and live sale fares are different animals — an average describes a whole month, while a sale fare applies to specific dates you must verify individually.

 The practical check sequence: pick your outbound and return dates, open the Low Fare Calendar for the LAX route, note the lowest fare shown per direction, then click through to the booking screen and confirm the complete round-trip total with taxes before committing. If the booking screen price differs from the calendar price, the booking screen is the one that counts.

 One more mechanism note: Southwest's own route pages for Denver–Phoenix and Phoenix–Denver advertise bundle options with hotels or rental cars. Bundling changes the terms of what you're buying, so if you see a bundled total, price the flight alone first so you know exactly what the flight portion costs before deciding whether the bundle adds value.

![calm autumn morning over Angeles coastal skyline soft](https://screenshots.mightytravels.com/article-images-ai/southwest-post-labor-day-fares-verify-la-ai-d0c31a77.jpg)

## Key Factors to Consider

 When you're sizing up a post-Labor Day sale fare from LAX to Denver or Phoenix, three criteria should drive the decision before anything else. First, direction matters: Southwest lists Denver-to-Phoenix and Phoenix-to-Denver as separate route pages on southwest.com, and pricing between the two directions is not guaranteed to match, so check both origin and destination in the booking flow rather than assuming symmetry. Second, one-way versus round-trip labeling: third-party listings such as Expedia and KAYAK quote Denver-Phoenix fares in both units — one-way and round-trip — and mixing them up is the fastest way to misjudge whether a sale price is actually a deal. Third, date flexibility: the Low Fare Calendar on Southwest's own site is the tool built for scanning which dates still price under your target, and it belongs in your workflow before you commit to any specific departure.

 The numbers that matter are the ones you verify in the live booking flow, not the ones in an ad. As priced above, KAYAK's route data shows December as the cheapest month for Southwest on Denver-to-Phoenix by average return fare — a seasonal benchmark, not a sale fare. Your check is simple: pull the same itinerary on Southwest's site, note the total with taxes included, and compare it like-for-like against the same unit (one-way against one-way, round-trip against round-trip) from the aggregator listing you saw.

 Baggage is the second number that matters, and it's one aggregators don't show. Southwest includes two free checked bags per passenger — a long-standing policy that comparison sources cite as saving travelers well over a hundred dollars per round trip versus carriers that charge bag fees. When you compare a Southwest total against a competitor's headline fare, add the competitor's bag fees to their number before you rank the options; otherwise you're comparing unlike totals.

 Bundling is the third factor. Southwest's own route pages for both Denver-Phoenix directions promote flight-plus-hotel and flight-plus-rental-car bundles as a way to find additional savings. If you were going to book a hotel or car anyway, price the bundle in the same session as the standalone flight and record both totals — but only after confirming the bundle's change and cancellation terms match what you'd get with the flight alone.

 One final criterion: recency of the price you're judging. Aggregator listings typically note that fares were available within the past seven days, which means the number you saw may already be stale by the time you book. Treat any third-party figure as a lead, run it through Southwest's booking flow the same day, and only commit when the live total — taxes, bags, and terms included — clears your threshold.

![Key Factors to Consider — Southwest post-Labor Day fares](https://screenshots.mightytravels.com/article-images-pixabay/southwest-post-labor-day-fares-verify-la-ef256db7.jpg)

## Common Mistakes

 The most common mistake I see is pricing a round-trip as two one-ways and assuming the total will match. Southwest's sale fares don't always price symmetrically: the outbound date you picked may show a sale rate while the return date prices at a regular fare, and the booking flow will happily sell you that mismatched combination. The fix is to run the full round-trip search with both dates selected and read the total on the payment screen — not the per-leg number on the results grid. If the round-trip total is more than double the one-way fare you saw advertised, one of your two legs is not actually on sale, and you should re-shop the return date before committing.

 The second pitfall is comparing Southwest's sale price against an aggregator screenshot instead of a like-for-like booking. Third-party sites list one-way fares from Denver to Phoenix starting at $43 and round-trips at $86, per Expedia, but those figures come with different terms: no free checked bags, no change flexibility, and a checkout flow that adds its own fees. Southwest's own route pages for Denver–Phoenix and Phoenix–Denver are where the sale terms actually live, and Southwest includes two free checked bags per passenger — a benefit KAYAK and Expedia listings don't bundle in. So when you compare, compare the complete option: fare plus bags plus change terms, all priced in the same booking flow. A fare that looks higher on Southwest's site can be cheaper in total once you add a checked bag to the third-party option.

 A related trap: trusting the route page headline instead of your actual dates. Southwest's Denver-to-Phoenix and Phoenix-to-Denver pages both advertise sale pricing "from" a base figure, but that figure is the cheapest date in the window, not your date — and as priced above, KAYAK's December average for Southwest on this route sits far above the advertised floor, so the spread can be enormous. The check is simple: enter your real travel pair, look at the Low Fare Calendar for the days surrounding your target, and only treat a date as "under $150 round-trip" if the calendar itself shows it.

 Finally, don't book the first total you see without checking the fare rules on the confirmation preview. Before you click purchase, confirm three things on that screen: the full round-trip total with taxes, the fare bucket or fare type shown, and whether both legs carry the sale terms. If any of the three is missing or looks off, back out and re-run the search — a sale fare that can't be verified in the live flow isn't a sale fare yet.

![Common Mistakes — Southwest post-Labor Day fares](https://screenshots.mightytravels.com/article-images-pixabay/southwest-post-labor-day-fares-verify-la-541cb66b.jpg)

## Insider Tactics

 One non-obvious tactic: price the trip in both directions before you assume the sale is symmetric. Southwest publishes Denver-to-Phoenix and Phoenix-to-Denver as separate route pages, and the two directions do not always carry the same lowest fare at the same moment. If your dates are flexible, run LAX–DEN and LAX–PHX as round-trips, then flip the order of the legs and compare the two totals side by side. A fare that looks unremarkable outbound can price lower when the return leg anchors the itinerary, and the only way to see that is to build both versions in the live booking flow rather than trusting a single search result.

 Timing tip: shop the Low Fare Calendar before you shop specific dates. Southwest's own booking tools include a Low Fare Calendar view, which lets you scan a month of departures at once instead of guessing date by date. Pull up the calendar for your route, note which days sit at the bottom of the range, then click through to confirm the full round-trip total — base fare plus taxes and fees — for the two or three cheapest candidates. The calendar shows you where to look; the booking flow tells you what you would actually pay.

 Treat every advertised number as a starting point, not a total. The benchmark figures already cited above — Expedia's $43 one-way / $86 round-trip and $89 one-way / $177 round-trip Southwest listings, and KAYAK's $273 December return average — come from different sellers, different dates, and different fare buckets, so none of them is a promise about your itinerary. Use them only as a rough sense of the range, then verify the live total yourself.

 Build a like-for-like comparison before you commit. Confirm the same passenger count, the same travel dates, and the same fare type on both the outbound and return before you judge a price. If one version of your itinerary includes a connection and the other is nonstop, you are not comparing the same product, and the cheaper-looking total may not be the better trip. Write down the full total for each candidate — not the headline fare — and keep the terms attached to it.

 Finally, check what the fare includes before you call it a deal. Southwest has long included two free checked bags, a benefit one source values at $140 or more per round-trip versus other airlines, but bundle offers that pair a flight with a hotel or rental car can change the effective cost of the trip. Price the flight alone first, then price the bundle, and compare the two totals rather than the marketing line. If the bundle is cheaper, confirm the hotel or car terms still match what you need before you book.

| Check | What to do |
| --- | --- |
| Direction | Price LAX–DEN and LAX–PHX round-trips both ways; compare totals |
| Timing | Scan the Low Fare Calendar, then confirm the full total in the booking flow |
| Like-for-like | Match dates, passengers, fare type, and nonstop vs. connecting |
| Inclusions | Price flight alone, then bundle; compare totals and terms |

![Insider Tactics — Southwest post-Labor Day fares](https://screenshots.mightytravels.com/article-images-pixabay/southwest-post-labor-day-fares-verify-la-fc7449ee.jpg)

## Comparison

 Put the two candidate itineraries side by side in the same Southwest booking flow before you decide anything. For the LAX–Denver and LAX–Phoenix round-trips in this sale, the comparison that matters is not the headline fare but the complete option: base fare plus any add-ons you would actually buy, priced as a round-trip, on the exact dates you would fly. The benchmark figures in the table below describe the Denver–Phoenix pair, not LAX, so treat them as a reference for how widely the same route can price depending on the seller and the month — then run your own LAX dates and compare like-for-like.

 Here is the side-by-side check, using the grounded Denver–Phoenix numbers as the reference row and your live LAX quotes as the challenger row:

| Option | One-way | Round-trip | Source |
| --- | --- | --- | --- |
| Expedia, Denver–Phoenix (lowest) | $43 | $86 | Expedia route page |
| Expedia, Southwest Denver–Phoenix | $89 | $177 | Expedia Southwest page |
| KAYAK, Southwest Denver–Phoenix, December average | — | $273 | KAYAK |
| Your LAX round-trip, live flow | — | Enter your dates | Southwest booking flow |

 The arithmetic rule is simple: a $43 one-way doubled is $86, which matches Expedia's round-trip figure exactly, so that pair is internally consistent. The $89 one-way doubled is $178, one dollar above the $177 round-trip Expedia lists — close enough that the round-trip is the better unit to quote. Never divide a round-trip figure to invent a one-way price, and never compare a one-way fare against a round-trip total; that mismatch is how a $43 fare starts looking like a $150 trip.

 Each option wins under a different condition. The lowest advertised fare wins only when your dates are flexible and you can accept the least convenient departure; Expedia's $43/$86 pair is the floor to beat. The Southwest-direct option wins when you want the fare bundled with the airline's own terms and you are pricing the round-trip as one unit — Expedia's $177 return for Southwest on Denver–Phoenix is the number to compare against your LAX total. The average-month figure wins as a reality check: if your LAX quote lands near KAYAK's $273 December average for Southwest on the Denver–Phoenix pair, you are paying typical, not sale, pricing. Southwest's own Denver–Phoenix and Phoenix–Denver route pages are the authoritative place to confirm what the carrier currently lists, and its two-free-checked-bags policy is worth pricing into the total if you would otherwise pay bag fees elsewhere.

 So the winner is whichever column shows the lower complete round-trip total for your exact dates after add-ons — not whichever headline number is smallest. Pull your LAX–Denver and LAX–Phoenix round-trips in the live flow, write the total in the last row, and commit only to the option that still beats the others once every term is included.

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## What to do next

## Frequently Asked Questions

 **Does Southwest's post-Labor Day sale book through Expedia or Kayak?**

 No — the sale works through Southwest's own booking flow, not through third-party aggregators.

 **Is Frontier cheaper than Southwest between Denver and Phoenix?**

 Yes — Expedia shows Frontier at $116 versus Southwest as the more expensive carrier on the DEN–PHX route.

 **When is the cheapest time of year to fly Southwest between Denver and Phoenix?**

 December is the cheapest month for Southwest on the DEN–PHX route, according to KAYAK's return-ticket averages.

 **Does the sale include a published list of discounted travel dates?**

 No — no such date list appears in the underlying fare data, so you have to check dates yourself in the live booking flow.

 **How current are the fares cited in this guide?**

 The prices were available within the past 7 days, and availability changes.

 **What should I check before committing to a fare I find?**

 Confirm the complete option in the live booking flow and compare like-for-like totals and terms before committing.

## Quick answers

| What is the starting price for Southwest round-trips between Denver and Phoenix? | Southwest round-trips between Denver and Phoenix have been listed starting at the $177 figure. |
| --- | --- |
| What one-way fares does Expedia list for Southwest on the DEN–PHX route? | Expedia lists Southwest one-way fares from the $89 or $43 figures depending on the listing. |
| What is the cheapest month for Southwest on the DEN–PHX route? | December is the cheapest month, with KAYAK reporting December return tickets averaging the $273 figure. |
| Which airline undercuts Southwest on DEN–PHX pricing? | Frontier undercuts Southwest, shown at the $116 figure versus Southwest's $177 figure as the cheapest carrier on the route. |
| What should readers do before committing to a fare? | Every fare must be verified in the live booking flow, confirming the complete option and comparing like-for-like totals and terms, since prices were available within the past 7 days and availability changes. |

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