Carrier route record
WNSEA→SJC
Southwest Airlines · Seattle to San Jose
- Flights
- 927
- Period
- July 2025 to June 2026
- Share of route
- 21%
- Carriers
- 5
Historical statistics for July 2025 to June 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, 5 points worse than the national rate of 77.6%. The late ones land about 45 minutes behind schedule. That rests on 927 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,562 at 88.0% on time.
The national on-time rate over the same period is 77.6%, so Southwest on SEA to SJC runs 5 points behind the country as a whole. Across a thousand flights that is about 50 extra late arrivals.
Key figures
On time
72.6%
Arrivals under 15 minutes late, of 924 completed flights
Avg delay
45 min
Across delayed arrivals only, not all flights
Cancelled
0.32%
National rate is 1.81%
Whole route
81.6%
Every carrier on SEA to SJC, 4,371 flights
These figures cover 927 flights between July 2025 and June 2026. The median arrival is 2 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 SEA to SJC
Southwest flew 927 of the 4,371 flights on SEA to SJC, about 21% of it. Its 72.6% on time is 9 points worse than the route as a whole, which runs 81.6%. Ranked by on-time rate it is last of five carriers on the route, where the range runs from American at 100.0% to Southwest at 72.6%. Two 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 88.0% of the time; Alaska Airlines manages 80.6%. Sample sizes sit next to every figure, because a two-point gap across 1,877 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlinesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| United Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,562 | 88.0% | 61 min | 0.19% | A+ |
| Alaska Airlines | 1,877 | 80.6% | 45 min | 1.55% | B |
| Southwest Airlines (this page) | 927 | 72.6% | 45 min | 0.32% | C+ |
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 49 points, against 7 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am124 flights90.2%
- 8am–11am237 flights94.5%
- 11am–2pm156 flights60.3%
- 2pm–5pm106 flights76.4%
- 5pm–8pm172 flights59.9%
- 8pm–5am132 flights45.5%
Scale runs 35% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 45.5% on time, against 94.5% 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 237 flights scheduled in it.
Across the year
Southwest on SEA to SJC through the year
June is the worst month at 54.0% on time, 38 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. July was the busiest month here, with 114 flights.
Across the week, Wednesday is the strongest day at 82.6% on time and Sunday the weakest at 66.2%. 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 63% 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.
- 63%Late-arriving aircraft
- 29%Carrier
- 7%National Airspace System
- 0%Security
- 0%Extreme weather
63% 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 63 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 11,351 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 94.5% on time here.
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
6.0% 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 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. 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 75.6% on time across 928 flights, 3 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 3 points of difference.
One caution: this is a thin sample. 927 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. 927 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 72.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 924 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 SJC88.0%
- Alaska Airlines on SEA to SJC80.6%
- 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 7.04 million flight records
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.