Carrier route record
WNSAN→SEA
Southwest Airlines · San Diego to Seattle
- Flights
- 118
- Period
- July 2025 to June 2026
- Share of route
- 3%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on SAN to SEA draws a D+. Roughly one flight in two arrives at least 15 minutes late, and the typical late arrival is roughly 45 minutes behind schedule. Build slack into anything you connect to. That rests on 118 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 1,700 at 87.3% on time.
The national on-time rate over the same period is 77.6%, so Southwest on SAN to SEA runs 19 points behind the country as a whole. Across a thousand flights that is about 195 extra late arrivals.
Key figures
On time
58.1%
Arrivals under 15 minutes late, of 117 completed flights
Avg delay
44 min
Across delayed arrivals only, not all flights
Cancelled
0.00%
National rate is 1.81%
Whole route
80.8%
Every carrier on SAN to SEA, 4,582 flights
These figures cover 118 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 SAN to SEA
Southwest flew 118 of the 4,582 flights on SAN to SEA, about 3% of it. Its 58.1% on time is 23 points worse than the route as a whole, which runs 80.8%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from Delta at 87.3% to SkyWest at 0.0%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 87.3% of the time; Alaska Airlines manages 77.8%. Sample sizes sit next to every figure, because a two-point gap across 2,763 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 1,700 | 87.3% | 76 min | 1.06% | A |
| Alaska Airlines | 2,763 | 77.8% | 61 min | 2.10% | B |
| Southwest Airlines (this page)thin sample | 118 | 58.1% | 44 min | 0.00% | D+ |
| SkyWest Airlinesthin sample | 1 | 0.0% | 28 min | 0.00% | F+ |
Delta 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 15 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am13 flights—
- 11am–2pm35 flights68.6%
- 2pm–5pm70 flights53.6%
- 5pm–8pm—
- 8pm–5am—
Scale runs 45% to 75%. Rows with fewer than 30 flights show a dash.
The best window here is not the first bank but the 11am–2pm slot at 68.6% on time, ahead of 2pm–5pm at 53.6%. Where the curve peaks mid-day rather than at dawn, the constraint is usually congestion at one end rather than the aircraft's own rotation. The 2pm–5pm window is the busiest, with 70 flights scheduled in it.
Across the year
Southwest on SAN to SEA through the year
- Jan–Mar 202627 flights—
- Apr–Jun 202691 flights57.8%
Scale runs 50% to 65%. Rows with fewer than 30 flights show a dash.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 58.1% on time across 118 flights.
Split by quarter, Southwest on SAN to SEA logged 27 flights in Jan–Mar 2026 and 91 flights in Apr–Jun 2026. Fewer than three of those quarters carried the 30 completed flights this site needs before printing a rate, so the 58.1% annual figure is the one to use.
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 2,138 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.
- 47%Late-arriving aircraft
- 31%Carrier
- 22%National Airspace System
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 2,138 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 2,138 reported delay minutes.
Cancellations are rare at 0.00%, below the national 1.81% 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
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 roughly 45 minutes, which a normal layover absorbs.
The 1,050 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 runs 55.9% on time across 118 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 118 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 SAN to SEA
Put together: treat all of this as provisional. 118 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 58.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 117 completed flights over 12 months sit behind that.
Related
Where to go next
- SAN to SEA, every carrier
- Southwest on SEA to SAN, the return leg
- Delta Air Lines on SAN to SEA87.3%
- Alaska Airlines on SAN to SEA77.8%
- Southwest Airlines network-wide record
- San Diego International (SAN) 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 7.04 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.