Carrier route record

WNSMF→DEN

Southwest Airlines · Sacramento to Denver

Flights: 1,864
Period: July 2025 to June 2026
Share of route: 49%
Carriers: 3

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on SMF 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 1,864 flights, with a median arrival right on schedule.

The US average over the same twelve months is 77.6%, so there is little to separate Southwest on SMF to DEN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

76.8%

Arrivals under 15 minutes late, of 1,848 completed flights

Avg delay

49 min

Across delayed arrivals only, not all flights

Cancelled

0.32%

National rate is 1.81%

Whole route

82.5%

Every carrier on SMF to DEN, 3,834 flights

These figures cover 1,864 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

Carrier by carrier

Southwest against every carrier on SMF to DEN

Southwest flew 1,864 of the 3,834 flights on SMF to DEN, about 49% of it. Its 76.8% on time is 6 points worse than the route as a whole, which runs 82.5%. 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 76.8%. 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.

On-time performance by carrier on SMF to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	1,797	88.3%	64 min	0.50%	A+
Frontier Airlinesthin sample	173	81.9%	72 min	0.58%	B+
Southwest Airlines (this page)	1,864	76.8%	49 min	0.32%	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 32 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–8am372 flights92.7%
8am–11am461 flights86.9%
11am–2pm286 flights71.9%
2pm–5pm430 flights61.2%
5pm–8pm215 flights67.9%
8pm–5am100 flights72.0%

Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 92.7% of the time, against 61.2% for the afternoon window. That is 32 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 461 flights scheduled in it.

Across the year

Southwest on SMF to DEN through the year

Darker means more delays. Figures are on-time percentages.February best, July worst

July is the worst month at 63.7% on time, 25 points below February, the best at 88.8%. 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 80.5% on time and Friday the weakest at 73.2%. 7 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 21,000 reported delay minutes.

Late-arriving aircraft
37%
National Airspace System
35%
Carrier
26%
Extreme weather
2%

37% 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 21,000 reported delay minutes here, that single category outweighs weather by 19 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 20,747 reported delay minutes.

35% 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 7,264 minutes out of 21,000, against a national NAS share of 21%.

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

6.2% 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 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 65.9% on time across 1,868 flights, 11 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 11 points of difference.

The sample behind these figures is 1,864 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 SMF to DEN

Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 88.8% on time and July 63.7%, a swing of 25 points. If the dates move at all, move them out of July before you think about anything else. 1,848 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures