Carrier route record
WNSEA→SJC
Southwest Airlines · Seattle to San Jose
- Flights
- 903
- 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 SEA to SJC sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 7 points worse than the national rate of 77.3%. The late ones land roughly 45 minutes behind schedule. That rests on 903 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,626 at 85.7% on time.
The national on-time rate over the same period is 77.3%, so Southwest on SEA to SJC runs 7 points behind the country as a whole. Across a thousand flights that is about 68 extra late arrivals.
Key figures
On time
70.5%
Arrivals under 15 minutes late, of 901 completed flights
Avg delay
46 min
Across delayed arrivals only, not all flights
Cancelled
0.22%
National rate is 1.89%
Whole route
80.1%
Every carrier on SEA to SJC, 4,425 flights
These figures cover 903 flights between September 2025 and August 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.
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Carrier by carrier
Southwest against every carrier on SEA to SJC
Southwest flew 903 of the 4,425 flights on SEA to SJC, about 20% of it. Its 70.5% on time is 10 points worse than the route as a whole, which runs 80.1%. Ranked by on-time rate it is last of six carriers on the route, where the range runs from United at 100.0% to Southwest at 70.5%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: 6 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Delta Air Linesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| American Airlinesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,626 | 85.7% | 59 min | 0.18% | A+ |
| Alaska Airlines | 1,887 | 79.8% | 44 min | 1.06% | B |
| Southwest Airlines (this page) | 903 | 70.5% | 46 min | 0.22% | C+ |
No carrier stands out. SkyWest tops the table at 85.7%, 6 points clear of the bottom, which is inside the range this kind of sample moves year to year.
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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 49 points, against 6 points between the best and worst carrier.
- 5am–8am133 flights86.4%
- 8am–11am202 flights95.0%
- 11am–2pm173 flights56.6%
- 2pm–5pm115 flights66.1%
- 5pm–8pm159 flights62.9%
- 8pm–5am121 flights46.3%
Scale runs 40% to 100%.
The 8pm–5am window is where this operation falls apart: 46.3% on time, against 95.0% for the 8am–11am 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 202 flights scheduled in it.
Across the year
Southwest on SEA to SJC through the year
August is the worst month at 52.7% on time, 39 points below January, the best at 92.1%. 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, Tuesday is the strongest day at 78.9% on time and Friday the weakest at 64.0%, a spread of 15 points.
Arrival by arrival
How late Southwest on SEA to SJC runs when it is late
The 266 late arrivals split 101 under half an hour, 101 between 30 and 60 minutes, and 64 an hour or more.
- 15+ min early160 flights17.8%
- Within 15 min475 flights52.7%
- 15–29 min late101 flights11.2%
- 30–59 min late101 flights11.2%
- 1–2 hours late54 flights6.0%
- 2+ hours late10 flights1.1%
Scale runs 0% to 100%.
Share of 901 completed flights by arrival against schedule.
69 of 307 late departures made up the time and arrived on time, 22% of them. 28 flights left on time and still arrived late.
The worst days
Worst days for Southwest on SEA to SJC
The latest arrival of the period was on 14 August 2026, 3 hours 30 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 14 August 2026 | 3 hours 30 minutes | Late-arriving aircraft |
| 1 December 2025 | 3 hours 22 minutes | Carrier |
| 17 October 2025 | 3 hours 13 minutes | Carrier |
| 6 November 2025 | 3 hours 5 minutes | Late-arriving aircraft |
| 23 June 2026 | 2 hours 43 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 62% of the 12,000 delay minutes carriers reported here, and the remaining four split what is left.
- 62%Late-arriving aircraft
- 29%Carrier
- 8%National Airspace System
- 1%Security
- 0%Extreme weather
62% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 12,000 reported delay minutes here, that single category outweighs weather by 62 to one. The split is drawn from 12,342 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 95.0% on time here.
Cancellations are rare at 0.22%, below the national 1.89% 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
7.1% 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 roughly 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 75.6% on time across 904 flights, 5 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 5 points of difference.
One caution: this is a thin sample. 903 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 SEA to SJC
Put together: treat all of this as provisional. 903 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 70.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 901 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to SJC, every carrier
- Southwest on SJC to SEA, the return leg
- SkyWest Airlines on SEA to SJC85.7%
- Alaska Airlines on SEA to SJC79.8%
- Southwest Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Norman Y. Mineta San Jose International (SJC) 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.