Carrier route record
ASSFO→SEA
Alaska Airlines · San Francisco to Seattle
- Flights
- 2,719
- Period
- July 2025 to June 2026
- Share of route
- 40%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Alaska Airlines.
Alaska on SFO to SEA sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land roughly 55 minutes behind schedule. That rests on 2,719 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 924 at 83.6% on time.
Delta Air Lines is the most reliable of the three carriers covered here at 83.6% on time across 924 flights.
Key figures
On time
69.1%
Arrivals under 15 minutes late, of 2,672 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
1.62%
National rate is 1.81%
Whole route
73.7%
Every carrier on SFO to SEA, 6,770 flights
These figures cover 2,719 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
Alaska against every carrier on SFO to SEA
Alaska flew 2,719 of the 6,770 flights on SFO to SEA, about 40% of it. Its 69.1% on time is 5 points worse than the route as a whole, which runs 73.7%. Ranked by on-time rate it is last of five carriers on the route, where the range runs from Southwest at 100.0% to Alaska at 69.1%. 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 83.6% of the time; SkyWest Airlines manages 72.7%. Sample sizes sit next to every figure, because a two-point gap across 1,082 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlinesthin sample | 3 | 100.0% | — | 0.00% | A+ |
| Delta Air Lines | 924 | 83.6% | 74 min | 1.73% | B |
| United Airlines | 2,042 | 75.8% | 58 min | 0.39% | B+ |
| SkyWest Airlines | 1,082 | 72.7% | 50 min | 1.11% | C |
| Alaska Airlines (this page) | 2,719 | 69.1% | 53 min | 1.62% | C |
Delta leads SkyWest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Alaska flight numbers on SFO to SEA
Departure window
When Alaska runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 28 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am377 flights87.1%
- 8am–11am517 flights59.5%
- 11am–2pm403 flights71.2%
- 2pm–5pm504 flights67.7%
- 5pm–8pm620 flights68.3%
- 8pm–5am298 flights63.9%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 87.1% of the time, against 59.5% for the morning window. That is 28 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 620 flights scheduled in it.
Across the year
Alaska on SFO to SEA through the year
July is the worst month at 56.5% on time, 34 points below February, the best at 90.2%. 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 280 flights.
Across the week, Tuesday is the strongest day at 75.4% on time and Friday the weakest at 63.8%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Alaska runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 53% of the 44,000 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.
- 53%Late-arriving aircraft
- 25%National Airspace System
- 22%Carrier
- 0%Extreme weather
53% 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 44,000 reported delay minutes here, that single category outweighs weather by 53 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 43,755 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 87.1% on time here.
Cancellations sit at 1.62% against a national 1.81%, which is ordinary. Diversions add another 0.11%.
Connections and stage length
What a delay here costs
7.5% 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 55 minutes, which a normal layover absorbs.
The 679 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 60.3% on time across 2,716 flights, 9 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 9 points of difference.
The sample behind these figures is 2,719 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 Alaska on SFO to SEA
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 90.2% on time and July 56.5%, a swing of 34 points. If the dates move at all, move them out of July before you think about anything else. 2,672 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to SEA, every carrier
- Alaska on SEA to SFO, the return leg
- Delta Air Lines on SFO to SEA83.6%
- United Airlines on SFO to SEA75.8%
- SkyWest Airlines on SFO to SEA72.7%
- Alaska Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
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.