Carrier route record
DLSAN→SEA
Delta Air Lines · San Diego to Seattle
- Flights
- 1,700
- Period
- July 2025 to June 2026
- Share of route
- 37%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on SAN to SEA earns an A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 10 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 1,700 flights, with a median arrival 12 minutes early.
Set against the rest of the country, Delta's SAN to SEA record is 10 points better than the US average of 77.6%. That gap is worth roughly 97 fewer late arrivals for every thousand flights.
Key figures
On time
87.3%
Arrivals under 15 minutes late, of 1,680 completed flights
Avg delay
76 min
Across delayed arrivals only, not all flights
Cancelled
1.06%
National rate is 1.81%
Whole route
80.8%
Every carrier on SAN to SEA, 4,582 flights
These figures cover 1,700 flights between July 2025 and June 2026. The median arrival is 12 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.
Carrier by carrier
Delta against every carrier on SAN to SEA
Delta flew 1,700 of the 4,582 flights on SAN to SEA, about 37% of it. Its 87.3% on time is 7 points better than the route as a whole, which runs 80.8%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from Delta at 87.3% to SkyWest at 0.0%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines (this page) | 1,700 | 87.3% | 76 min | 1.06% | A |
| Alaska Airlines | 2,763 | 77.8% | 61 min | 2.10% | B |
| Southwest Airlinesthin sample | 118 | 58.1% | 44 min | 0.00% | D+ |
| SkyWest Airlinesthin sample | 1 | 0.0% | 28 min | 0.00% | F+ |
Flight by flight
Delta flight numbers on SAN to SEA
Departure window
When Delta runs best on this route
Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 1,700 flights.
- 5am–8am365 flights90.9%
- 8am–11am—
- 11am–2pm630 flights87.2%
- 2pm–5pm393 flights87.1%
- 5pm–8pm312 flights83.7%
- 8pm–5am—
Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.
The early departures do better, though not dramatically: 90.9% on time for the 5am–8am window against 83.7% for 5pm–8pm. Worth taking if the schedule allows, not worth an extra connection. The 11am–2pm window is the busiest, with 630 flights scheduled in it.
Across the year
Delta on SAN to SEA through the year
Delays peak in November, when the on-time rate falls to 81.5%. February is the strongest month at 93.4%. Moving a flexible trip across that boundary buys 12 points. May was the busiest month here, with 150 flights.
Across the week, Tuesday is the strongest day at 91.5% on time and Thursday the weakest at 82.3%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Delta runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 53% of the 16,000 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.
- 53%Late-arriving aircraft
- 31%Carrier
- 16%National Airspace System
- 0%Extreme weather
53% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 16,000 reported delay minutes here, that single category outweighs weather by 53 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 16,162 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 90.9% on time here.
Cancellations sit at 1.06% against a national 1.81%, which is ordinary. Diversions add another 0.12%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.9% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
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. 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 82.6% on time across 1,700 flights, 5 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 5 points of difference.
The sample behind these figures is 1,700 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 Delta on SAN to SEA
Put together: take the 5am–8am departure, avoid November if the dates are flexible, and if two carriers are within a few dollars of each other, Alaska is the one with the record behind it. None of that guarantees an on-time arrival; it moves the odds by 7 points, which is the most any booking decision can do. 1,680 completed flights over 12 months sit behind that.
Related
Where to go next
- SAN to SEA, every carrier
- Delta on SEA to SAN, the return leg
- Alaska Airlines on SAN to SEA77.8%
- Southwest Airlines on SAN to SEA58.1%
- Delta Air Lines network-wide record
- San Diego International (SAN) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Why the first flight of the morning is statistically safest
- Worst months to fly in the US, ranked by the data
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.