Carrier route record
ASSEA→SFO
Alaska Airlines · Seattle to San Francisco
- Flights
- 2,716
- 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 SEA to SFO draws a D. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 50 minutes behind schedule. Build slack into anything you connect to. That rests on 2,716 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,081 at 75.4% on time.
SkyWest Airlines is the most reliable of the three carriers covered here at 75.4% on time across 1,081 flights.
Key figures
On time
60.3%
Arrivals under 15 minutes late, of 2,677 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
1.40%
National rate is 1.81%
Whole route
65.6%
Every carrier on SEA to SFO, 6,764 flights
These figures cover 2,716 flights between July 2025 and June 2026. Beyond the headline rate, 11.2% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Alaska against every carrier on SEA to SFO
Alaska flew 2,716 of the 6,764 flights on SEA to SFO, about 40% of it. Its 60.3% on time is 5 points worse than the route as a whole, which runs 65.6%. 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 60.3%. 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 75.4% of the time; United Airlines manages 66.5%. Sample sizes sit next to every figure, because a two-point gap across 2,040 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 | 1,081 | 75.4% | 53 min | 1.02% | B |
| Delta Air Lines | 923 | 67.3% | 56 min | 1.63% | C |
| United Airlines | 2,040 | 66.5% | 71 min | 0.83% | C+ |
| Alaska Airlines (this page) | 2,716 | 60.3% | 52 min | 1.40% | D |
SkyWest leads United by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 25 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am205 flights43.4%
- 8am–11am334 flights61.2%
- 11am–2pm610 flights68.3%
- 2pm–5pm431 flights67.3%
- 5pm–8pm672 flights54.1%
- 8pm–5am464 flights59.0%
Scale runs 35% 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 68.3% on time, ahead of 5am–8am at 43.4%. 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 672 flights scheduled in it.
Across the year
Alaska on SEA to SFO through the year
Delays peak in May, when the on-time rate falls to 34.9%. January is the strongest month at 78.4%. Moving a flexible trip across that boundary buys 44 points. July was the busiest month here, with 280 flights.
Across the week, Wednesday is the strongest day at 68.1% on time and Sunday the weakest at 52.5%. 16 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. National Airspace System accounts for 51% of the 56,000 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.
- 51%National Airspace System
- 24%Late-arriving aircraft
- 20%Carrier
- 5%Extreme weather
- 0%Security
51% 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 29,000 minutes out of 56,000, against a national NAS share of 21%. The split is drawn from 55,655 reported delay minutes.
Cancellations sit at 1.40% against a national 1.81%, which is ordinary. Diversions add another 0.04%.
Connections and stage length
What a delay here costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 11.2% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum 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. 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 69.1% on time across 2,719 flights, 9 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 9 points of difference.
The sample behind these figures is 2,716 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 May 34.9%, a swing of 44 points. If the dates move at all, move them out of May before you think about anything else. 2,677 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 SFO75.4%
- Delta Air Lines on SEA to SFO67.3%
- United Airlines on SEA to SFO66.5%
- Alaska Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- San Francisco International (SFO) delay statistics
- The best time of day to fly, according to 7.04 million flight records
- How often a connection fails at the major US hubs
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.