Carrier route record
WNSJC→SEA
Southwest Airlines · San Jose to Seattle
- Flights
- 904
- Period
- September 2025 to August 2026
- Share of route
- 20%
- Carriers
- 6
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SJC to SEA sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.3%. The late ones land about 45 minutes behind schedule. That rests on 904 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,627 at 88.7% on time.
The US average over the same twelve months is 77.3%, so there is little to separate Southwest on SJC to SEA from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
75.6%
Arrivals under 15 minutes late, of 903 completed flights
Avg delay
46 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.89%
Whole route
82.7%
Every carrier on SJC to SEA, 4,422 flights
These figures cover 904 flights between September 2025 and August 2026. The median arrival is 4 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.
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Carrier by carrier
Southwest against every carrier on SJC to SEA
Southwest flew 904 of the 4,422 flights on SJC to SEA, about 20% of it. Its 75.6% on time is 7 points worse than the route as a whole, which runs 82.7%. Ranked by on-time rate it is last of six carriers on the route, where the range runs from Delta at 100.0% to Southwest at 75.6%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 88.7% of the time; Alaska Airlines manages 80.7%. Sample sizes sit next to every figure, because a two-point gap across 1,884 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Linesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| American Airlinesthin sample | 2 | 100.0% | — | 0.00% | A+ |
| United Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,627 | 88.7% | 63 min | 0.18% | A+ |
| Alaska Airlines | 1,884 | 80.7% | 51 min | 1.27% | B |
| Southwest Airlines (this page) | 904 | 75.6% | 46 min | 0.00% | B+ |
SkyWest leads Alaska by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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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 38 points, against 8 points between the best and worst carrier.
- 5am–8am235 flights97.9%
- 8am–11am105 flights74.3%
- 11am–2pm125 flights61.6%
- 2pm–5pm133 flights84.2%
- 5pm–8pm167 flights62.3%
- 8pm–5am139 flights59.7%
Scale runs 50% to 100%.
The 8pm–5am window is where this operation falls apart: 59.7% on time, against 97.9% 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 235 flights scheduled in it.
Across the year
Southwest on SJC to SEA through the year
August is the worst month at 61.3% on time, 31 points below January, the best at 92.3%. 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. August was the busiest month here, with 93 flights.
Across the week, Wednesday is the strongest day at 85.3% on time and Sunday the weakest at 60.8%, a spread of 25 points.
Arrival by arrival
How late Southwest on SJC to SEA runs when it is late
Southwest on SJC to SEA often beats the schedule: 230 of 903 completed flights, 25%, arrived 15 minutes or more early. The 220 late arrivals split 86 under half an hour, 81 between 30 and 60 minutes, and 53 an hour or more.
- 15+ min early230 flights25.5%
- Within 15 min453 flights50.2%
- 15–29 min late86 flights9.5%
- 30–59 min late81 flights9.0%
- 1–2 hours late45 flights5.0%
- 2+ hours late8 flights0.9%
Scale runs 0% to 100%.
Share of 903 completed flights by arrival against schedule.
57 of 234 late departures made up the time and arrived on time, 24% of them. 43 flights left on time and still arrived late.
The worst days
Worst days for Southwest on SJC to SEA
The latest arrival of the period was on 17 February 2026, 4 hours 48 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 17 February 2026 | 4 hours 48 minutes | Late-arriving aircraft |
| 19 December 2025 | 3 hours 10 minutes | Late-arriving aircraft |
| 30 October 2025 | 2 hours 47 minutes | Late-arriving aircraft |
| 12 December 2025 | 2 hours 15 minutes | Late-arriving aircraft |
| 29 November 2025 | 2 hours 9 minutes | Carrier |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 54% of the 10,000 delay minutes carriers reported here, and the remaining four split what is left.
- 54%Late-arriving aircraft
- 23%Carrier
- 23%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. Across 10,000 reported delay minutes here, that single category outweighs weather by 54 to one. The split is drawn from 10,027 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 97.9% on time here.
Cancellations are rare at 0.00%, below the national 1.89% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
5.9% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about 45 minutes, which a normal layover absorbs.
The 696 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.
The return leg is a different operation and performs like one: it runs 70.5% on time across 903 flights, 5 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 5 points of difference.
One caution: this is a thin sample. 904 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Southwest on SJC to SEA
Put together: treat all of this as provisional. 904 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 75.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 903 completed flights over 12 months sit behind that.
Related
Where to go next
- SJC to SEA, every carrier
- Southwest on SEA to SJC, the return leg
- SkyWest Airlines on SJC to SEA88.7%
- Alaska Airlines on SJC to SEA80.7%
- Southwest Airlines network-wide record
- Norman Y. Mineta San Jose International (SJC) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.