Carrier route record
WNSFO→DEN
Southwest Airlines · San Francisco to Denver
- Flights
- 1,436
- 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 SFO to DEN draws a D+. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 1,436 flights. The strongest carrier on the route with a full sample, United Airlines, flew 3,370 at 82.2% on time.
The national on-time rate over the same period is 77.6%, so Southwest on SFO to DEN runs 17 points behind the country as a whole. Across a thousand flights that is about 171 extra late arrivals.
Key figures
On time
60.5%
Arrivals under 15 minutes late, of 1,419 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
0.70%
National rate is 1.81%
Whole route
75.5%
Every carrier on SFO to DEN, 5,410 flights
These figures cover 1,436 flights between July 2025 and June 2026. Beyond the headline rate, 12.6% 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 SFO to DEN
Southwest flew 1,436 of the 5,410 flights on SFO to DEN, about 27% of it. Its 60.5% on time is 15 points worse than the route as a whole, which runs 75.5%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from United at 82.2% to Southwest at 60.5%.
The choice of carrier is not cosmetic here. United Airlines arrives on time 82.2% of the time; Frontier Airlines manages 73.2%. Sample sizes sit next to every figure, because a two-point gap across 604 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 3,370 | 82.2% | 59 min | 0.27% | B+ |
| Frontier Airlines | 604 | 73.2% | 61 min | 0.99% | C+ |
| Southwest Airlines (this page) | 1,436 | 60.5% | 58 min | 0.70% | D+ |
United leads Frontier 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 57 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am374 flights93.5%
- 8am–11am303 flights66.9%
- 11am–2pm300 flights42.6%
- 2pm–5pm305 flights36.7%
- 5pm–8pm131 flights50.4%
- 8pm–5am23 flights—
Scale runs 30% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.5% of the time, against 36.7% for the afternoon window. That is 57 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 374 flights scheduled in it.
Across the year
Southwest on SFO to DEN through the year
June is the worst month at 38.2% on time, 44 points below January, the best at 81.9%. 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 70.2% on time and Friday the weakest at 53.8%. 16 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 54% of the 32,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 54%Late-arriving aircraft
- 24%Carrier
- 21%National Airspace System
- 1%Extreme weather
54% 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 32,000 reported delay minutes here, that single category outweighs weather by 54 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 32,439 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 93.5% on time here.
Cancellations are rare at 0.70%, 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. 12.6% 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 52.6% on time across 1,438 flights, 8 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 8 points of difference.
The sample behind these figures is 1,436 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 SFO to DEN
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 81.9% on time and June 38.2%, a swing of 44 points. If the dates move at all, move them out of June before you think about anything else. 1,419 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to DEN, every carrier
- Southwest on DEN to SFO, the return leg
- United Airlines on SFO to DEN82.2%
- Frontier Airlines on SFO to DEN73.2%
- Southwest Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Denver International (DEN) 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.