Route reliability record
SAN→SEA
San Diego to Seattle
- Flights
- 4,646
- Period
- September 2025 to August 2026
- Distance
- 1,050 mi
- Carriers
- 4
This route lands a B, 4 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 4,646 SAN to SEA flights, of which Delta Air Lines flew 1,710 at 86.6% on time.
Best time to fly SAN to SEA: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 90.7% of the time and Tuesday flights 88.7%, against 81.1% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
81.1%
Arrivals under 15 minutes late, of 4,576 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
1.42%
National rate is 1.89%
Best carrier
Delta
86.6% on time across 1,710 flights
These figures cover 4,646 flights between September 2025 and August 2026. The median arrival is 9 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 SAN to SEA
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 86.6% of the time; Alaska Airlines manages 79.5%. 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 |
|---|---|---|---|---|---|
| Delta Air Lines | 1,710 | 86.6% | 77 min | 1.11% | A |
| Alaska Airlines | 2,727 | 79.5% | 60 min | 1.72% | B |
| Southwest Airlinesthin sample | 208 | 56.5% | 49 min | 0.00% | D+ |
| SkyWest Airlinesthin sample | 1 | 0.0% | 28 min | 0.00% | F+ |
Delta leads Alaska by 7 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on SAN 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 Diego to Seattle
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SAN → SEASan Diego to Seattle | Delta Air Lines | 85.6% | 86.6% | 1.11% | 5am–8am, Tue | DL 2530 07:30 |
| 2. SAN → SEASan Diego to Seattle | Alaska Airlines | 78.1% | 79.5% | 1.72% | 5am–8am, Tue | — |
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 14 points, against 7 points between the best and worst carrier.
- 5am–8am874 flights90.7%
- 8am–11am428 flights80.0%
- 11am–2pm1,136 flights82.5%
- 2pm–5pm1,091 flights76.9%
- 5pm–8pm910 flights76.5%
- 8pm–5am207 flights77.3%
Scale runs 70% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 90.7% of the time, against 76.5% for the evening window. That is 14 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 1,136 flights scheduled in it.
Explore
Filter SAN 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 SAN to SEA, the best departure window is 5am–8am at 90.7% on time and the worst is 5pm–8pm at 76.5%, a wide gap of 14.2 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am90.7%
- 8–11am80.0%
- 11am–2pm82.5%
- 2–5pm76.9%
- 5–8pm76.5%
- 8pm–5am77.3%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 21 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.
August is the worst month at 71.2% on time, 21 points below February, the best at 92.1%. 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 479 flights.
Across the week, Tuesday is the strongest day at 88.7% on time and Friday the weakest at 74.8%, a spread of 14 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 54% of the 55,000 delay minutes carriers reported here, and the remaining four split what is left.
- 54%Late-arriving aircraft
- 30%Carrier
- 15%National Airspace System
- 1%Extreme weather
- 0%Security
54% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 55,000 reported delay minutes here, that single category outweighs weather by 54 to one. The split is drawn from 54,877 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 90.7% on time here.
Cancellations sit at 1.42% against a national 1.89%, which is ordinary. Diversions add another 0.09%.
Connections and stage length
What a delay here actually costs
5.6% 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 1,050 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 75.0% on time across 4,647 flights, 6 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 6 points of difference.
The sample behind these figures is 4,646 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. February runs 92.1% on time and August 71.2%, a swing of 21 points. If the dates move at all, move them out of August before you think about anything else. 4,576 completed flights over 12 months sit behind that.
Common questions
SAN to SEA questions
How often is SAN to SEA delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 18.9% of the 4,646 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on SAN to SEA?
Delta Air Lines leads at 86.6% on time across 1,710 flights. Alaska Airlines is at the other end on 79.5%, a gap of 7 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 SAN to SEA?
The 5am–8am departure window is the strongest at 90.7% on time. The 5pm–8pm window is the weakest at 76.5%, 14 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 August delays on SAN to SEA?
August is the weakest month at 71.2% on time, compared with 92.1% in February. Across the year that is 21 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 SAN — the return legseparate record
- San Diego International (SAN) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Delta Air Lines on SAN to SEA86.6%
- Alaska Airlines on SAN to SEA79.5%
- Southwest Airlines on SAN to SEA56.5%
- SAN to SFO, a related route59.5%
- LAX to SEA, a related route85.0%
- SAN to DEN, a related route78.4%
- Delta Air Lines on-time record86.6%
- Alaska Airlines on-time record79.5%
- Southwest Airlines on-time record56.5%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. SAN to SEA and SEA to SAN 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.