Carrier route record

WNSEA→SMF

Southwest Airlines · Seattle to Sacramento

Flights: 1,156
Period: July 2025 to June 2026
Share of route: 26%
Carriers: 3

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

Southwest on SEA to SMF sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 6 points worse than the national rate of 77.6%. The late ones land roughly 50 minutes behind schedule. That rests on 1,156 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,941 at 89.3% on time.

The national on-time rate over the same period is 77.6%, so Southwest on SEA to SMF runs 6 points behind the country as a whole. Across a thousand flights that is about 57 extra late arrivals.

On time

71.9%

Arrivals under 15 minutes late, of 1,148 completed flights

Avg delay

48 min

Across delayed arrivals only, not all flights

Cancelled

0.43%

National rate is 1.81%

Whole route

81.9%

Every carrier on SEA to SMF, 4,407 flights

These figures cover 1,156 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 SEA to SMF

Southwest flew 1,156 of the 4,407 flights on SEA to SMF, about 26% of it. Its 71.9% on time is 10 points worse than the route as a whole, which runs 81.9%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 89.3% to Southwest at 71.9%.

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 89.3% of the time; Alaska Airlines manages 79.8%. Sample sizes sit next to every figure, because a two-point gap across 1,310 flights means less than a ten-point one.

On-time performance by carrier on SEA to SMF
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	1,941	89.3%	62 min	0.26%	A+
Alaska Airlines	1,310	79.8%	44 min	0.61%	B+
Southwest Airlines (this page)	1,156	71.9%	48 min	0.43%	C+

SkyWest leads Alaska by 10 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 51 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am376 flights95.7%
8am–11am90 flights83.1%
11am–2pm223 flights62.8%
2pm–5pm101 flights45.0%
5pm–8pm220 flights60.7%
8pm–5am146 flights53.4%

Scale runs 35% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 95.7% of the time, against 45.0% for the afternoon window. That is 51 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 376 flights scheduled in it.

Across the year

Southwest on SEA to SMF through the year

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

July is the worst month at 60.3% on time, 24 points below January, the best at 84.5%. 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 127 flights.

Across the week, Wednesday is the strongest day at 77.8% on time and Friday the weakest at 66.1%. 12 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 66% of the 15,000 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.

Late-arriving aircraft
66%
Carrier
27%
National Airspace System
7%
Security
1%
Extreme weather
0%

66% 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 15,000 reported delay minutes here, that single category outweighs weather by 66 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 15,345 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 95.7% on time here.

Cancellations are rare at 0.43%, 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

6.3% 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 605 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 77.4% on time across 1,155 flights, 6 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 6 points of difference.

The sample behind these figures is 1,156 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 SEA to SMF

Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 84.5% on time and July 60.3%, a swing of 24 points. If the dates move at all, move them out of July before you think about anything else. 1,148 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