Route reliability record
SEA→SFO
Seattle to San Francisco
- Flights
- 6,817
- Period
- September 2025 to August 2026
- Distance
- 679 mi
- Carriers
- 5
This route draws a D. Roughly one flight in two arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 6,817 SEA to SFO flights, of which SkyWest Airlines flew 1,039 at 69.9% on time.
Best time to fly SEA to SFO: a 2pm–5pm departure, ideally on a Saturday. Flights in that window arrived on time 68.2% of the time and Saturday flights 68.3%, against 59.8% for the route overall.
SkyWest Airlines is the most reliable of the four carriers covered here at 69.9% on time across 1,039 flights.
Key figures
On time
59.8%
Arrivals under 15 minutes late, of 6,739 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
1.11%
National rate is 1.89%
Best carrier
SkyWest
69.9% on time across 1,039 flights
These figures cover 6,817 flights between September 2025 and August 2026. Beyond the headline rate, 11.9% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on SEA to SFO
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 69.9% of the time; Alaska Airlines manages 56.0%. Sample sizes sit next to every figure, because a two-point gap across 2,727 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 | 2,727 | 56.0% | 52 min | 1.14% | D |
The spread between SkyWest and Alaska is 14 points, wide enough that it should decide the booking. On a hundred trips that is 14 more arrivals inside the on-time window.
Flight by flight
Flights on SEA to SFO
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
- United 73719:3753.9% · 362 flights
- Delta 141210:2560.1% · 346 flights
- Delta 263521:2069.6% · 340 flights
- SkyWest 370713:4068.5% · 325 flights
- Alaska 65511:4267.2% · 305 flights
- Alaska 72507:0350.5% · 299 flights
- SkyWest 399116:2559.9% · 296 flights
- Alaska 68013:2065.5% · 280 flights
- Alaska 138515:4867.7% · 263 flights
- United 148210:2966.3% · 256 flights
- Alaska 52808:5350.2% · 250 flights
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Best ways to make this trip
The most reliable ways to fly Seattle to San Francisco
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 5 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SEA → SJCSeattle to San Jose | SkyWest Airlines | 85.5% | 85.7% | 0.18% | 8am–11am, Tue | OO 3736 08:30 |
| 2. SEA → SJCSeattle to San Jose | Alaska Airlines | 79.0% | 79.8% | 1.06% | 5am–8am, Wed | — |
| 3. SEA → OAKSeattle to Oakland | Alaska Airlines | 77.3% | 78.3% | 1.27% | 5am–8am, Mon | AS 706 21:45 |
| 4. SEA → SJCSeattle to San Jose | Southwest Airlines | 70.3% | 70.5% | 0.22% | 8am–11am, Tue | — |
| 5. SEA → OAKSeattle to Oakland | Southwest Airlines | 69.6% | 69.8% | 0.28% | 5am–8am, Wed | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 points, against 14 points between the best and worst carrier.
- 5am–8am1,155 flights60.5%
- 8am–11am1,007 flights49.9%
- 11am–2pm1,351 flights68.1%
- 2pm–5pm885 flights68.2%
- 5pm–8pm1,624 flights52.8%
- 8pm–5am795 flights61.8%
Scale runs 40% to 75%.
The best window here is not the first bank but the 2pm–5pm slot at 68.2% on time, ahead of 8am–11am at 49.9%. 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 1,624 flights scheduled in it.
Explore
Filter SEA to SFO by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On SEA to SFO, the best departure window is 2pm–5pm at 68.2% on time and the worst is 8am–11am at 49.9%, a wide gap of 18.3 points. All US flights leaving 2pm–5pm ran 71.9%.
- 5–8am60.5%
- 8–11am49.9%
- 11am–2pm68.1%
- 2–5pm68.2%
- 5–8pm52.8%
- 8pm–5am61.8%
best all US flightsScale 40% to 95%.
Across the year
When delays peak on this route
This route's year swings by 47 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 35.0% on time, 47 points below March, the best at 81.7%. 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 666 flights.
Across the week, Saturday is the strongest day at 68.3% on time and Monday the weakest at 54.0%, a spread of 14 points.
Delay causes
Why this route gets delayed
National Airspace System accounts for 58% of the 154,000 delay minutes carriers reported here, and the remaining four split what is left.
- 58%National Airspace System
- 21%Carrier
- 18%Late-arriving aircraft
- 4%Extreme weather
- 0%Security
58% 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 89,000 minutes out of 154,000, against a national NAS share of 21%. The split is drawn from 153,566 reported delay minutes.
Cancellations sit at 1.11% against a national 1.89%, which is ordinary. Diversions add another 0.03%.
Connections and stage length
What a delay here actually costs
11.9% 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 72.3% on time across 6,821 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 6,817 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.
Work out the risk of missing a connection in SFO after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. March runs 81.7% on time and July 35.0%, a swing of 47 points. If the dates move at all, move them out of July before you think about anything else. 6,739 completed flights over 12 months sit behind that.
Common questions
SEA to SFO questions
How often is SEA to SFO delayed?
Roughly one flight in two arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 40.2% of the 6,817 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SEA to SFO?
SkyWest Airlines leads at 69.9% on time across 1,039 flights. Alaska Airlines is at the other end on 56.0%, a gap of 14 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on SEA to SFO?
The 2pm–5pm departure window is the strongest at 68.2% on time. The 8am–11am window is the weakest at 49.9%, 18 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on SEA to SFO?
July is the weakest month at 35.0% on time, compared with 81.7% in March. Across the year that is 47 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SFO to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- San Francisco International (SFO) delay statistics
- SkyWest Airlines on SEA to SFO69.9%
- Delta Air Lines on SEA to SFO60.5%
- United Airlines on SEA to SFO59.1%
- Alaska Airlines on SEA to SFO56.0%
- SEA to LAX, a related route82.0%
- LAX to SFO, a related route60.1%
- SEA to PHX, a related route78.2%
- Southwest Airlines on-time record100.0%
- SkyWest Airlines on-time record69.9%
- Delta Air Lines on-time record60.5%
- 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
Direction matters. SEA to SFO and SFO to SEA are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.