Carrier route record
WNDEN→SFO
Southwest Airlines · Denver to San Francisco
- Flights
- 1,438
- Period
- July 2025 to June 2026
- Share of route
- 27%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on DEN to SFO earns an F+, which is as low as this site's scale goes for a reason. Only 52.6% of flights arrive inside the 15-minute window, 25 points worse than the national rate of 77.6%. Late arrivals average about an hour. Treat any tight connection here as a coin flip. That rests on 1,438 flights. The strongest carrier on the route with a full sample, United Airlines, flew 3,373 at 71.2% on time.
The national on-time rate over the same period is 77.6%, so Southwest on DEN to SFO runs 25 points behind the country as a whole. Across a thousand flights that is about 250 extra late arrivals.
Key figures
On time
52.6%
Arrivals under 15 minutes late, of 1,430 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
0.49%
National rate is 1.81%
Whole route
65.8%
Every carrier on DEN to SFO, 5,415 flights
These figures cover 1,438 flights between July 2025 and June 2026. Beyond the headline rate, 18.9% 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 DEN to SFO
Southwest flew 1,438 of the 5,415 flights on DEN to SFO, about 27% of it. Its 52.6% on time is 13 points worse than the route as a whole, which runs 65.8%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from United at 71.2% to Southwest at 52.6%.
The two carriers here are closely matched: 4 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 |
|---|---|---|---|---|---|
| United Airlines | 3,373 | 71.2% | 63 min | 0.42% | C+ |
| Frontier Airlines | 604 | 67.2% | 55 min | 0.83% | C+ |
| Southwest Airlines (this page) | 1,438 | 52.6% | 59 min | 0.49% | F+ |
No carrier stands out. United tops the table at 71.2%, 4 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 23 points, against 4 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am72 flights44.4%
- 8am–11am301 flights60.3%
- 11am–2pm275 flights52.6%
- 2pm–5pm198 flights67.3%
- 5pm–8pm199 flights45.5%
- 8pm–5am393 flights44.4%
Scale runs 35% to 75%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 44.4% on time, against 67.3% for the 2pm–5pm slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8pm–5am window is the busiest, with 393 flights scheduled in it.
Across the year
Southwest on DEN to SFO through the year
June is the worst month at 10.9% on time, 69 points below January, the best at 80.2%. 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 139 flights.
Across the week, Tuesday is the strongest day at 62.0% on time and Thursday the weakest at 44.4%. 18 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 40,000 reported delay minutes.
- 39%National Airspace System
- 35%Late-arriving aircraft
- 23%Carrier
- 3%Extreme weather
35% 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 40,000 reported delay minutes here, that single category outweighs weather by 11 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 40,203 reported delay minutes.
39% 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 16,000 minutes out of 40,000, against a national NAS share of 21%.
Cancellations are rare at 0.49%, 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
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 18.9% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
The 967 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 60.5% on time across 1,436 flights, 8 points above 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 8 points of difference.
The sample behind these figures is 1,438 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 DEN to SFO
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 80.2% on time and June 10.9%, a swing of 69 points. If the dates move at all, move them out of June before you think about anything else. 1,430 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to SFO, every carrier
- Southwest on SFO to DEN, the return leg
- United Airlines on DEN to SFO71.2%
- Frontier Airlines on DEN to SFO67.2%
- Southwest Airlines network-wide record
- Denver International (DEN) delay statistics
- San Francisco International (SFO) delay statistics
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
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.