Carrier route record
WNTUS→DEN
Southwest Airlines · Tucson to Denver
- Flights
- 1,202
- Period
- July 2025 to June 2026
- Share of route
- 44%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on TUS to DEN lands a B+, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,202 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 621 at 86.5% on time.
The US average over the same twelve months is 77.6%, so there is little to separate Southwest on TUS to DEN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.1%
Arrivals under 15 minutes late, of 1,193 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.58%
National rate is 1.81%
Whole route
82.9%
Every carrier on TUS to DEN, 2,754 flights
These figures cover 1,202 flights between July 2025 and June 2026. The median arrival is 4 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Carrier by carrier
Southwest against every carrier on TUS to DEN
Southwest flew 1,202 of the 2,754 flights on TUS to DEN, about 44% of it. Its 80.1% on time is 3 points worse than the route as a whole, which runs 82.9%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from SkyWest at 86.5% to Southwest at 80.1%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: 2 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlines | 621 | 86.5% | 93 min | 0.64% | A+ |
| United Airlines | 836 | 84.7% | 73 min | 0.60% | B+ |
| Frontier Airlinesthin sample | 95 | 80.9% | 52 min | 1.05% | B |
| Southwest Airlines (this page) | 1,202 | 80.1% | 61 min | 0.58% | B+ |
No carrier stands out. SkyWest tops the table at 86.5%, 2 points clear of the bottom, which is inside the range this kind of sample moves year to year.
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 32 points, against 2 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am331 flights93.6%
- 8am–11am326 flights85.1%
- 11am–2pm163 flights82.8%
- 2pm–5pm342 flights61.7%
- 5pm–8pm40 flights70.0%
- 8pm–5am—
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.6% of the time, against 61.7% for the afternoon window. That is 32 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 342 flights scheduled in it.
Across the year
Southwest on TUS to DEN through the year
July is the worst month at 68.5% on time, 20 points below January, the best at 88.7%. 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. October was the busiest month here, with 117 flights.
Across the week, Saturday is the strongest day at 85.6% on time and Tuesday the weakest at 76.8%. 9 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 15,000 reported delay minutes.
- 37%Late-arriving aircraft
- 35%National Airspace System
- 22%Carrier
- 5%Extreme weather
- 0%Security
37% 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 15,000 reported delay minutes here, that single category outweighs weather by 7 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 14,518 reported delay minutes.
35% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 5,102 minutes out of 15,000, against a national NAS share of 21%.
Cancellations are rare at 0.58%, 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
6.9% 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 639 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 is a different operation and performs like one: it runs 70.6% on time across 1,202 flights, 10 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 10 points of difference.
The sample behind these figures is 1,202 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 TUS to DEN
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 88.7% on time and July 68.5%, a swing of 20 points. If the dates move at all, move them out of July before you think about anything else. 1,193 completed flights over 12 months sit behind that.
Related
Where to go next
- TUS to DEN, every carrier
- Southwest on DEN to TUS, the return leg
- SkyWest Airlines on TUS to DEN86.5%
- United Airlines on TUS to DEN84.7%
- Southwest Airlines network-wide record
- 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.