Carrier route record
ASSEA→SFO
Alaska Airlines · Seattle to San Francisco
- Flights
- 2,727
- Period
- September 2025 to August 2026
- Share of route
- 40%
- Carriers
- 5
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Alaska Airlines.
Alaska on SEA to SFO earns a D, which is as low as this site's scale goes for a reason. Only 56.0% of flights arrive inside the 15-minute window, 21 points worse than the national rate of 77.3%. Late arrivals average roughly 50 minutes. Treat any tight connection here as a coin flip. That rests on 2,727 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,039 at 69.9% on time.
SkyWest Airlines is the most reliable of the three carriers covered here at 69.9% on time across 1,039 flights.
Key figures
On time
56.0%
Arrivals under 15 minutes late, of 2,696 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
1.14%
National rate is 1.89%
Whole route
59.8%
Every carrier on SEA to SFO, 6,817 flights
These figures cover 2,727 flights between September 2025 and August 2026. Beyond the headline rate, 12.2% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Alaska against every carrier on SEA to SFO
Alaska flew 2,727 of the 6,817 flights on SEA to SFO, about 40% of it. Its 56.0% on time is 4 points worse than the route as a whole, which runs 59.8%. 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 56.0%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 69.9% of the time; United Airlines manages 59.1%. Sample sizes sit next to every figure, because a two-point gap across 2,062 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlinesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,039 | 69.9% | 52 min | 1.06% | C |
| Delta Air Lines | 985 | 60.5% | 54 min | 1.73% | D |
| United Airlines | 2,062 | 59.1% | 67 min | 0.82% | D+ |
| Alaska Airlines (this page) | 2,727 | 56.0% | 52 min | 1.14% | D |
SkyWest leads United 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 SEA to SFO
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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.
- 5am–8am218 flights39.2%
- 8am–11am349 flights54.7%
- 11am–2pm621 flights67.5%
- 2pm–5pm394 flights65.6%
- 5pm–8pm704 flights45.8%
- 8pm–5am441 flights56.6%
Scale runs 30% to 75%.
The best window here is not the first bank but the 11am–2pm slot at 67.5% on time, ahead of 5am–8am at 39.2%. 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 5pm–8pm window is the busiest, with 704 flights scheduled in it.
Across the year
Alaska on SEA to SFO through the year
July is the worst month at 33.5% on time, 45 points below January, the best at 78.4%. 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 283 flights.
Across the week, Tuesday is the strongest day at 66.7% on time and Sunday the weakest at 50.6%, a spread of 16 points.
Arrival by arrival
How late Alaska on SEA to SFO runs when it is late
The 1,186 late arrivals split 393 under half an hour, 463 between 30 and 60 minutes, and 330 an hour or more.
- 15+ min early333 flights12.4%
- Within 15 min1,177 flights43.7%
- 15–29 min late393 flights14.6%
- 30–59 min late463 flights17.2%
- 1–2 hours late259 flights9.6%
- 2+ hours late71 flights2.6%
Scale runs 0% to 100%.
Share of 2,696 completed flights by arrival against schedule.
146 of 1,092 late departures made up the time and arrived on time, 13% of them. In the other direction, 240 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SFO.
The worst days
Worst days for Alaska on SEA to SFO
The latest arrival of the period was on 21 March 2026, 7 hours 49 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 21 March 2026 | 7 hours 49 minutes | Carrier |
| 31 May 2026 | 4 hours 29 minutes | Carrier |
| 11 September 2025 | 4 hours 25 minutes | Carrier |
| 5 December 2025 | 3 hours 52 minutes | Carrier |
| 13 March 2026 | 3 hours 48 minutes | Late-arriving aircraft |
Delay causes
Why Alaska runs late on this route
National Airspace System accounts for 61% of the 61,000 delay minutes carriers reported here, and the remaining four split what is left.
- 61%National Airspace System
- 20%Late-arriving aircraft
- 15%Carrier
- 4%Extreme weather
61% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 37,000 minutes out of 61,000, against a national NAS share of 21%. The split is drawn from 61,045 reported delay minutes.
Cancellations sit at 1.14% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
12.2% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
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.
The return leg is a different operation and performs like one: it runs 68.8% on time across 2,729 flights, 13 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 13 points of difference.
The sample behind these figures is 2,727 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 SEA to SFO
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 78.4% on time and July 33.5%, a swing of 45 points. If the dates move at all, move them out of July before you think about anything else. 2,696 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to SFO, every carrier
- Alaska on SFO to SEA, the return leg
- SkyWest Airlines on SEA to SFO69.9%
- Delta Air Lines on SEA to SFO60.5%
- United Airlines on SEA to SFO59.1%
- Alaska Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- San Francisco International (SFO) delay statistics
- Same route, different airline: where the carrier you pick matters most
- 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.