Carrier route record
WNPHX→DEN
Southwest Airlines · Phoenix to Denver
- Flights
- 3,942
- Period
- July 2025 to June 2026
- Share of route
- 44%
- Carriers
- 6
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on PHX to DEN sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 3,942 flights. The strongest carrier on the route with a full sample, United Airlines, flew 2,370 at 83.5% on time.
United Airlines is the most reliable of the three carriers covered here at 83.5% on time across 2,370 flights.
Key figures
On time
72.8%
Arrivals under 15 minutes late, of 3,900 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
0.81%
National rate is 1.81%
Whole route
77.2%
Every carrier on PHX to DEN, 8,920 flights
These figures cover 3,942 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Southwest against every carrier on PHX to DEN
Southwest flew 3,942 of the 8,920 flights on PHX to DEN, about 44% of it. Its 72.8% on time is 4 points worse than the route as a whole, which runs 77.2%. Ranked by on-time rate it is number five of six carriers on the route, where the range runs from United at 83.5% to SkyWest at 66.7%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. United Airlines arrives on time 83.5% of the time; American Airlines manages 74.8%. Sample sizes sit next to every figure, because a two-point gap across 974 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 2,370 | 83.5% | 75 min | 0.59% | B+ |
| Envoy Airthin sample | 189 | 81.8% | 53 min | 0.53% | B+ |
| Frontier Airlines | 1,427 | 80.0% | 88 min | 0.63% | B+ |
| American Airlines | 974 | 74.8% | 66 min | 0.62% | C+ |
| Southwest Airlines (this page) | 3,942 | 72.8% | 56 min | 0.81% | C+ |
| SkyWest Airlinesthin sample | 18 | 66.7% | 98 min | 0.00% | C+ |
United leads American by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 37 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am804 flights93.0%
- 8am–11am734 flights83.0%
- 11am–2pm678 flights71.7%
- 2pm–5pm789 flights56.5%
- 5pm–8pm563 flights61.0%
- 8pm–5am374 flights63.3%
Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.0% of the time, against 56.5% for the afternoon window. That is 37 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 804 flights scheduled in it.
Across the year
Southwest on PHX to DEN through the year
July is the worst month at 62.0% on time, 20 points below January, the best at 81.8%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. March was the busiest month here, with 386 flights.
Across the week, Saturday is the strongest day at 79.9% on time and Sunday the weakest at 66.5%. 13 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 59,000 reported delay minutes.
- 41%Late-arriving aircraft
- 29%National Airspace System
- 28%Carrier
- 2%Extreme weather
- 0%Security
41% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 59,000 reported delay minutes here, that single category outweighs weather by 18 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 59,366 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 93.0% on time here.
Cancellations are rare at 0.81%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
8.2% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, which a normal layover absorbs.
The 602 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg runs 72.1% on time across 3,950 flights, within half a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 3,942 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
What to do with this
Booking Southwest on PHX to DEN
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 81.8% on time and July 62.0%, a swing of 20 points. If the dates move at all, move them out of July before you think about anything else. 3,900 completed flights over 12 months sit behind that.
Related
Where to go next
- PHX to DEN, every carrier
- Southwest on DEN to PHX, the return leg
- United Airlines on PHX to DEN83.5%
- Envoy Air on PHX to DEN81.8%
- Frontier Airlines on PHX to DEN80.0%
- American Airlines on PHX to DEN74.8%
- Southwest Airlines network-wide record
- Phoenix Sky Harbor International (PHX) delay statistics
- Denver International (DEN) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.