Carrier route record
WNDEN→SMF
Southwest Airlines · Denver to Sacramento
- Flights
- 1,868
- Period
- July 2025 to June 2026
- Share of route
- 49%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on DEN to SMF draws a C+. About one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 55 minutes behind schedule. Build slack into anything you connect to. That rests on 1,868 flights, with a median arrival 4 minutes late.
The national on-time rate over the same period is 77.6%, so Southwest on DEN to SMF runs 12 points behind the country as a whole. Across a thousand flights that is about 117 extra late arrivals.
Key figures
On time
65.9%
Arrivals under 15 minutes late, of 1,862 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
0.32%
National rate is 1.81%
Whole route
73.5%
Every carrier on DEN to SMF, 3,839 flights
These figures cover 1,868 flights between July 2025 and June 2026. Beyond the headline rate, 10.5% 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 SMF
Southwest flew 1,868 of the 3,839 flights on DEN to SMF, about 49% of it. Its 65.9% on time is 8 points worse than the route as a whole, which runs 73.5%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from SkyWest at 100.0% to Southwest at 65.9%. Two 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 |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Frontier Airlinesthin sample | 173 | 81.9% | 53 min | 0.58% | B+ |
| United Airlines | 1,797 | 80.6% | 62 min | 0.33% | B+ |
| Southwest Airlines (this page) | 1,868 | 65.9% | 53 min | 0.32% | C+ |
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 45 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–8am110 flights90.0%
- 8am–11am459 flights86.3%
- 11am–2pm324 flights72.4%
- 2pm–5pm302 flights57.3%
- 5pm–8pm232 flights45.5%
- 8pm–5am441 flights50.3%
Scale runs 35% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 45.5% on time, against 90.0% for the 5am–8am 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 8am–11am window is the busiest, with 459 flights scheduled in it.
Across the year
Southwest on DEN to SMF through the year
June is the worst month at 44.7% on time, 36 points below February, the best at 80.8%. 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 196 flights.
Across the week, Wednesday is the strongest day at 71.4% on time and Thursday the weakest at 57.2%. 14 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 56% of the 34,000 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.
- 56%Late-arriving aircraft
- 35%Carrier
- 8%National Airspace System
- 1%Extreme weather
- 0%Security
56% 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 34,000 reported delay minutes here, that single category outweighs weather by 56 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 33,916 reported delay minutes.
The largest share of delay minutes, 35%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 12,000 of the 34,000 delay minutes reported here.
Cancellations are rare at 0.32%, 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. 10.5% 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 909 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 76.8% on time across 1,864 flights, 11 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 11 points of difference.
The sample behind these figures is 1,868 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 SMF
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 80.8% on time and June 44.7%, a swing of 36 points. If the dates move at all, move them out of June before you think about anything else. 1,862 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to SMF, every carrier
- Southwest on SMF to DEN, the return leg
- Frontier Airlines on DEN to SMF81.9%
- United Airlines on DEN to SMF80.6%
- Southwest Airlines network-wide record
- Denver International (DEN) delay statistics
- Sacramento International (SMF) 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.