Carrier route record

WNSMF→SEA

Southwest Airlines · Sacramento to Seattle

Flights: 1,155
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 SMF to SEA lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by roughly 45 minutes on average. That is a workable record, not a spotless one. That rests on 1,155 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,952 at 87.4% on time.

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

On time

77.4%

Arrivals under 15 minutes late, of 1,153 completed flights

Avg delay

43 min

Across delayed arrivals only, not all flights

Cancelled

0.17%

National rate is 1.81%

Whole route

82.7%

Every carrier on SMF to SEA, 4,416 flights

These figures cover 1,155 flights between July 2025 and June 2026. The median arrival is 3 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Southwest against every carrier on SMF to SEA

Southwest flew 1,155 of the 4,416 flights on SMF to SEA, about 26% of it. Its 77.4% on time is 5 points worse than the route as a whole, which runs 82.7%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 87.4% to Southwest at 77.4%.

The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 87.4% of the time; Alaska Airlines manages 80.3%. Sample sizes sit next to every figure, because a two-point gap across 1,309 flights means less than a ten-point one.

On-time performance by carrier on SMF to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	1,952	87.4%	57 min	0.26%	A+
Alaska Airlines	1,309	80.3%	42 min	0.61%	B+
Southwest Airlines (this page)	1,155	77.4%	43 min	0.17%	B+

SkyWest leads Alaska by 7 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 36 points, against 7 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am347 flights95.1%
8am–11am68 flights64.7%
11am–2pm161 flights66.5%
2pm–5pm158 flights73.9%
5pm–8pm125 flights59.2%
8pm–5am296 flights74.9%

Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 59.2% on time, against 95.1% 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 5am–8am window is the busiest, with 347 flights scheduled in it.

Across the year

Southwest on SMF to SEA through the year

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

June is the worst month at 65.1% on time, 25 points below January, the best at 90.5%. 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 85.8% on time and Sunday the weakest at 69.7%. 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 47% of the 11,000 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
47%
Carrier
32%
National Airspace System
20%
Extreme weather
0%
Security
0%

47% 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 11,000 reported delay minutes here, that single category outweighs weather by 47 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 11,101 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 95.1% on time here.

Cancellations are rare at 0.17%, 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

5.0% 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 45 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 71.9% on time across 1,156 flights, 6 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 6 points of difference.

The sample behind these figures is 1,155 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 SEA

Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 90.5% on time and June 65.1%, a swing of 25 points. If the dates move at all, move them out of June before you think about anything else. 1,153 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