Carrier route record
WNSJC→DEN
Southwest Airlines · San Jose to Denver
- Flights
- 1,527
- Period
- July 2025 to June 2026
- Share of route
- 59%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SJC to DEN lands a B+, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 1,527 flights, with a median arrival 3 minutes early.
The US average over the same twelve months is 77.6%, 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
76.3%
Arrivals under 15 minutes late, of 1,516 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
0.46%
National rate is 1.81%
Whole route
81.0%
Every carrier on SJC to DEN, 2,579 flights
These figures cover 1,527 flights between July 2025 and June 2026. The median arrival is 3 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 SJC to DEN
Southwest flew 1,527 of the 2,579 flights on SJC to DEN, most of the route. Its 76.3% on time is 5 points worse than the route as a whole, which runs 81.0%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from United at 88.3% to Southwest at 76.3%. 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 | 998 | 88.3% | 68 min | 0.40% | A+ |
| Frontier Airlinesthin sample | 54 | 81.5% | 45 min | 0.00% | B+ |
| Southwest Airlines (this page) | 1,527 | 76.3% | 52 min | 0.46% | B+ |
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 38 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am345 flights95.9%
- 8am–11am317 flights88.6%
- 11am–2pm268 flights70.6%
- 2pm–5pm373 flights58.1%
- 5pm–8pm185 flights64.9%
- 8pm–5am39 flights71.8%
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 95.9% of the time, against 58.1% for the afternoon window. That is 38 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 373 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 150 flights.
Across the week, Saturday is the strongest day at 85.4% on time and Thursday the weakest at 69.5%. 16 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 19,000 reported delay minutes.
- 36%Late-arriving aircraft
- 34%National Airspace System
- 26%Carrier
- 2%Extreme weather
- 1%Security
36% 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 19,000 reported delay minutes here, that single category outweighs weather by 17 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 18,845 reported delay minutes.
34% 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 6,490 minutes out of 19,000, against a national NAS share of 21%.
Cancellations are rare at 0.46%, 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
6.5% 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 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. 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 69.4% on time across 1,529 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 1,527 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. 1,516 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 DEN88.3%
- 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 7.04 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.