Route reliability record
SFO→SEA
San Francisco to Seattle
- Flights
- 6,821
- Period
- September 2025 to August 2026
- Distance
- 679 mi
- Carriers
- 5
This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 6,821 SFO to SEA flights, of which Delta Air Lines flew 986 at 79.5% on time.
Best time to fly SFO to SEA: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 91.7% of the time and Saturday flights 80.3%, against 72.3% for the route overall.
Delta Air Lines is the most reliable of the four carriers covered here at 79.5% on time across 986 flights.
Key figures
On time
72.3%
Arrivals under 15 minutes late, of 6,740 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
1.08%
National rate is 1.89%
Best carrier
Delta
79.5% on time across 986 flights
These figures cover 6,821 flights between September 2025 and August 2026. The median arrival is 3 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
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Carrier by carrier
Which airline is most reliable on SFO to SEA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 79.5% of the time; SkyWest Airlines manages 68.8%. Sample sizes sit next to every figure, because a two-point gap across 1,040 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 | 986 | 79.5% | 70 min | 1.83% | B |
| United Airlines | 2,063 | 75.1% | 57 min | 0.44% | B+ |
| Alaska Airlines | 2,729 | 68.8% | 54 min | 1.28% | C |
| SkyWest Airlines | 1,040 | 68.8% | 50 min | 1.15% | 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
Flights on SFO to SEA
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.
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Best ways to make this trip
The most reliable ways to fly San Francisco to Seattle
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. 4 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SJC → SEASan Jose to Seattle | SkyWest Airlines | 88.5% | 88.7% | 0.18% | 5am–8am, Sat | OO 4041 07:15 |
| 2. OAK → SEAOakland to Seattle | Alaska Airlines | 80.6% | 81.9% | 1.53% | 5am–8am, Sat | AS 705 07:00 |
| 3. SJC → SEASan Jose to Seattle | Alaska Airlines | 79.7% | 80.7% | 1.27% | 5am–8am, Wed | AS 1311 10:19 |
| 4. SFO → SEASan Francisco to Seattle | Delta Air Lines | 78.0% | 79.5% | 1.83% | 5am–8am, Sun | DL 2721 05:55 |
| 5. SJC → SEASan Jose to Seattle | Southwest Airlines | 75.6% | 75.6% | 0.00% | 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 27 points, against 11 points between the best and worst carrier.
- 5am–8am920 flights91.7%
- 8am–11am1,272 flights65.0%
- 11am–2pm896 flights72.6%
- 2pm–5pm1,480 flights72.9%
- 5pm–8pm1,177 flights70.6%
- 8pm–5am1,076 flights65.1%
Scale runs 55% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.7% of the time, against 65.0% for the morning window. That is 27 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 2pm–5pm window is the busiest, with 1,480 flights scheduled in it.
Explore
Filter SFO to SEA 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 SFO to SEA, the best departure window is 5am–8am at 91.7% on time and the worst is 8am–11am at 65.0%, a wide gap of 26.7 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am91.7%
- 8–11am65.0%
- 11am–2pm72.6%
- 2–5pm72.9%
- 5–8pm70.6%
- 8pm–5am65.1%
best all US flightsScale 55% to 95%.
Across the year
When delays peak on this route
This route's year swings by 27 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.
June is the worst month at 60.1% on time, 27 points below March, the best at 86.9%. 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 80.3% on time and Thursday the weakest at 65.6%, a spread of 15 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 47% of the 104,000 delay minutes carriers reported here, and the remaining four split what is left.
- 47%Late-arriving aircraft
- 26%Carrier
- 22%National Airspace System
- 4%Extreme weather
47% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 104,000 reported delay minutes here, that single category outweighs weather by 13 to one. The split is drawn from 103,971 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 91.7% on time here.
Cancellations sit at 1.08% against a national 1.89%, which is ordinary. Diversions add another 0.10%.
Connections and stage length
What a delay here actually costs
7.6% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last about an hour, 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.
The return leg is a different operation and performs like one: it runs 59.8% on time across 6,817 flights, 13 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 13 points of difference.
The sample behind these figures is 6,821 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 SEA 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 86.9% on time and June 60.1%, a swing of 27 points. If the dates move at all, move them out of June before you think about anything else. 6,740 completed flights over 12 months sit behind that.
Common questions
SFO to SEA questions
How often is SFO to SEA delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.7% of the 6,821 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SFO to SEA?
Delta Air Lines leads at 79.5% on time across 986 flights. SkyWest Airlines is at the other end on 68.8%, a gap of 11 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 SFO to SEA?
The 5am–8am departure window is the strongest at 91.7% on time. The 8am–11am window is the weakest at 65.0%, 27 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 June delays on SFO to SEA?
June is the weakest month at 60.1% on time, compared with 86.9% in March. Across the year that is 27 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
- SEA to SFO — the return legseparate record
- San Francisco International (SFO) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on SFO to SEA79.5%
- United Airlines on SFO to SEA75.1%
- Alaska Airlines on SFO to SEA68.8%
- SkyWest Airlines on SFO to SEA68.8%
- SFO to LAX, a related route70.9%
- LAX to SEA, a related route85.0%
- SFO to JFK, a related route78.0%
- Southwest Airlines on-time record100.0%
- Delta Air Lines on-time record79.5%
- United Airlines on-time record75.1%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. SFO to SEA and SEA to SFO 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.