Carrier route record
WNSJC→DEN
Southwest Airlines · San Jose to Denver
- Flights
- 1,520
- Period
- September 2025 to August 2026
- Share of route
- 60%
- Carriers
- 3
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SJC to DEN sits in the middle of the pack with a C+. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.3%. The late ones land roughly 50 minutes behind schedule. That rests on 1,520 flights, with a median arrival 2 minutes early.
The US average over the same twelve months is 77.3%, so there is little to separate Southwest on SJC 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
74.8%
Arrivals under 15 minutes late, of 1,509 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
0.46%
National rate is 1.89%
Whole route
80.6%
Every carrier on SJC to DEN, 2,546 flights
These figures cover 1,520 flights between September 2025 and August 2026. The median arrival is 2 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.
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Carrier by carrier
Southwest against every carrier on SJC to DEN
Southwest flew 1,520 of the 2,546 flights on SJC to DEN, most of the route. Its 74.8% on time is 6 points worse than the route as a whole, which runs 80.6%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from United at 89.3% to Southwest at 74.8%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 992 | 89.3% | 68 min | 0.30% | A+ |
| Frontier Airlinesthin sample | 34 | 85.3% | 47 min | 0.00% | A+ |
| Southwest Airlines (this page) | 1,520 | 74.8% | 52 min | 0.46% | C+ |
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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 39 points, against half a point between the best and worst carrier.
- 5am–8am332 flights96.0%
- 8am–11am317 flights87.7%
- 11am–2pm240 flights68.6%
- 2pm–5pm374 flights57.3%
- 5pm–8pm214 flights61.7%
- 8pm–5am43 flights69.8%
Scale runs 50% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 96.0% of the time, against 57.3% for the afternoon window. That is 39 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 374 flights scheduled in it.
Across the year
Southwest on SJC to DEN through the year
June is the worst month at 53.2% on time, 40 points below January, the best at 93.5%. 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. July was the busiest month here, with 151 flights.
Across the week, Tuesday is the strongest day at 84.5% on time and Thursday the weakest at 67.4%, a spread of 17 points.
Arrival by arrival
How late Southwest on SJC to DEN runs when it is late
The 380 late arrivals split 151 under half an hour, 130 between 30 and 60 minutes, and 99 an hour or more.
- 15+ min early221 flights14.6%
- Within 15 min908 flights60.2%
- 15–29 min late151 flights10.0%
- 30–59 min late130 flights8.6%
- 1–2 hours late72 flights4.8%
- 2+ hours late27 flights1.8%
Scale runs 0% to 100%.
Share of 1,509 completed flights by arrival against schedule.
73 of 392 late departures made up the time and arrived on time, 19% of them. 61 flights left on time and still arrived late.
The worst days
Worst days for Southwest on SJC to DEN
The latest arrival of the period was on 24 April 2026, 10 hours 39 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). Three of the five worst days fell in August 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 24 April 2026 | 10 hours 39 minutes | Carrier |
| 15 March 2026 | 5 hours 29 minutes | Carrier |
| 14 August 2026 | 5 hours 21 minutes | National Airspace System |
| 23 August 2026 | 4 hours 17 minutes | Late-arriving aircraft |
| 13 August 2026 | 3 hours 19 minutes | Late-arriving aircraft |
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 20,000 reported delay minutes.
- 37%Late-arriving aircraft
- 31%National Airspace System
- 29%Carrier
- 2%Extreme weather
- 1%Security
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 20,000 reported delay minutes here, that single category outweighs weather by 18 to one. The split is drawn from 19,573 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 96.0% on time here.
Cancellations are rare at 0.46%, below the national 1.89% 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
6.6% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last roughly 50 minutes, which a normal layover absorbs.
The 948 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.
The return leg is a different operation and performs like one: it runs 68.0% on time across 1,523 flights, 7 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 7 points of difference.
The sample behind these figures is 1,520 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 SJC to DEN
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 93.5% on time and June 53.2%, a swing of 40 points. If the dates move at all, move them out of June before you think about anything else. 1,509 completed flights over 12 months sit behind that.
Related
Where to go next
- SJC to DEN, every carrier
- Southwest on DEN to SJC, the return leg
- United Airlines on SJC to DEN89.3%
- Southwest Airlines network-wide record
- Norman Y. Mineta San Jose International (SJC) 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 7.05 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.