Route reliability record
SEA→SAN
Seattle to San Diego
- Flights
- 4,647
- Period
- September 2025 to August 2026
- Distance
- 1,050 mi
- Carriers
- 4
This route sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.3%. The late ones land roughly 45 minutes behind schedule. That rests on 4,647 SEA to SAN flights, of which Delta Air Lines flew 1,710 at 81.1% on time.
Best time to fly SEA to SAN: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 88.0% of the time and Tuesday flights 84.3%, against 75.0% 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
75.0%
Arrivals under 15 minutes late, of 4,587 completed flights
Avg delay
47 min
Across delayed arrivals only, not all flights
Cancelled
0.90%
National rate is 1.89%
Best carrier
Delta
81.1% on time across 1,710 flights
These figures cover 4,647 flights between September 2025 and August 2026. The median arrival is 2 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 SEA to SAN
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 81.1% of the time; Alaska Airlines manages 73.3%. Sample sizes sit next to every figure, because a two-point gap across 2,728 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| SkyWest Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Delta Air Lines | 1,710 | 81.1% | 51 min | 0.94% | B+ |
| Alaska Airlines | 2,728 | 73.3% | 45 min | 0.95% | C+ |
| Southwest Airlinesthin sample | 208 | 47.1% | 45 min | 0.00% | F+ |
Delta leads Alaska by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on SEA to SAN
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 Seattle to San Diego
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. SEA → SANSeattle to San Diego | Delta Air Lines | 80.3% | 81.1% | 0.94% | 5am–8am, Tue | DL 2508 07:15 |
| 2. SEA → SANSeattle to San Diego | Alaska Airlines | 72.6% | 73.3% | 0.95% | 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 25 points, against 8 points between the best and worst carrier.
- 5am–8am716 flights88.0%
- 8am–11am782 flights74.8%
- 11am–2pm882 flights75.3%
- 2pm–5pm1,002 flights74.6%
- 5pm–8pm773 flights62.8%
- 8pm–5am492 flights75.3%
Scale runs 55% to 95%.
The 5pm–8pm window is where this operation falls apart: 62.8% on time, against 88.0% for the 5am–8am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 2pm–5pm window is the busiest, with 1,002 flights scheduled in it.
Explore
Filter SEA to SAN 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 SAN, the best departure window is 5am–8am at 88.0% on time and the worst is 5pm–8pm at 62.8%, a wide gap of 25.2 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am88.0%
- 8–11am74.8%
- 11am–2pm75.3%
- 2–5pm74.6%
- 5–8pm62.8%
- 8pm–5am75.3%
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.
August is the worst month at 60.6% on time, 27 points below April, the best at 88.0%. 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 478 flights.
Across the week, Tuesday is the strongest day at 84.3% on time and Sunday the weakest at 68.3%, a spread of 16 points.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 54,000 reported delay minutes.
- 36%National Airspace System
- 33%Carrier
- 28%Late-arriving aircraft
- 3%Extreme weather
- 0%Security
36% 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 20,000 minutes out of 54,000, against a national NAS share of 21%. The split is drawn from 53,691 reported delay minutes.
Cancellations sit at 0.90% against a national 1.89%, which is ordinary. Diversions add another 0.39%.
Connections and stage length
What a delay here actually costs
5.2% 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 roughly 45 minutes, 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 81.1% on time across 4,646 flights, 6 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 6 points of difference.
The sample behind these figures is 4,647 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 SAN 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. April runs 88.0% on time and August 60.6%, a swing of 27 points. If the dates move at all, move them out of August before you think about anything else. 4,587 completed flights over 12 months sit behind that.
Common questions
SEA to SAN questions
How often is SEA to SAN delayed?
About 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 25.0% of the 4,647 flights in this analysis, against 22.7% nationally. Delayed flights are late by roughly 45 minutes on average.
Which airline is most reliable on SEA to SAN?
Delta Air Lines leads at 81.1% on time across 1,710 flights. Alaska Airlines is at the other end on 73.3%, a gap of 8 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 SAN?
The 5am–8am departure window is the strongest at 88.0% on time. The 5pm–8pm window is the weakest at 62.8%, 25 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 SEA to SAN?
August is the weakest month at 60.6% on time, compared with 88.0% in April. 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
- SAN to SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- San Diego International (SAN) delay statistics
- Delta Air Lines on SEA to SAN81.1%
- Alaska Airlines on SEA to SAN73.3%
- Southwest Airlines on SEA to SAN47.1%
- SEA to LAX, a related route82.0%
- SFO to SAN, a related route62.2%
- SEA to PHX, a related route78.2%
- SkyWest Airlines on-time record100.0%
- Delta Air Lines on-time record81.1%
- Alaska Airlines on-time record73.3%
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SEA to SAN and SAN 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.