Carrier route record
ASSJC→SEA
Alaska Airlines · San Jose to Seattle
- Flights
- 1,884
- Period
- September 2025 to August 2026
- Share of route
- 43%
- Carriers
- 6
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Alaska Airlines.
Alaska on SJC to SEA lands a B, 3 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 50 minutes on average. That rests on 1,884 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,627 at 88.7% on time.
The US average over the same twelve months is 77.3%, so there is little to separate Alaska on SJC to SEA from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.7%
Arrivals under 15 minutes late, of 1,860 completed flights
Avg delay
51 min
Across delayed arrivals only, not all flights
Cancelled
1.27%
National rate is 1.89%
Whole route
82.7%
Every carrier on SJC to SEA, 4,422 flights
These figures cover 1,884 flights between September 2025 and August 2026. The median arrival is 7 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
Alaska against every carrier on SJC to SEA
Alaska flew 1,884 of the 4,422 flights on SJC to SEA, about 43% of it. Its 80.7% on time is 2 points worse than the route as a whole, which runs 82.7%. Ranked by on-time rate it is number five of six carriers on the route, where the range runs from Delta at 100.0% to Southwest at 75.6%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. SkyWest Airlines arrives on time 88.7% of the time; Southwest Airlines manages 75.6%. Sample sizes sit next to every figure, because a two-point gap across 904 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Linesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| American Airlinesthin sample | 2 | 100.0% | — | 0.00% | A+ |
| United Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,627 | 88.7% | 63 min | 0.18% | A+ |
| Alaska Airlines (this page) | 1,884 | 80.7% | 51 min | 1.27% | B |
| Southwest Airlines | 904 | 75.6% | 46 min | 0.00% | B+ |
The spread between SkyWest and Southwest is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.
Flight by flight
Alaska flight numbers on SJC to SEA
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Departure window
When Alaska runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 points, against 13 points between the best and worst carrier.
- 5am–8am206 flights93.7%
- 8am–11am557 flights76.1%
- 11am–2pm183 flights92.9%
- 2pm–5pm364 flights81.7%
- 5pm–8pm496 flights75.3%
- 8pm–5am78 flights79.2%
Scale runs 65% to 100%.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.7% of the time, against 75.3% for the evening window. That is 18 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 557 flights scheduled in it.
Across the year
Alaska on SJC to SEA through the year
June is the worst month at 67.5% on time, 28 points below February, the best at 95.5%. 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 191 flights.
Across the week, Wednesday is the strongest day at 86.2% on time and Thursday the weakest at 73.8%, a spread of 12 points.
Arrival by arrival
How late Alaska on SJC to SEA runs when it is late
Alaska on SJC to SEA often beats the schedule: 609 of 1,860 completed flights, 33%, arrived 15 minutes or more early. The 359 late arrivals split 153 under half an hour, 113 between 30 and 60 minutes, and 93 an hour or more.
- 15+ min early609 flights32.7%
- Within 15 min892 flights48.0%
- 15–29 min late153 flights8.2%
- 30–59 min late113 flights6.1%
- 1–2 hours late72 flights3.9%
- 2+ hours late21 flights1.1%
Scale runs 0% to 100%.
Share of 1,860 completed flights by arrival against schedule.
81 of 321 late departures made up the time and arrived on time, 25% of them. In the other direction, 119 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SEA.
The worst days
Worst days for Alaska on SJC to SEA
The latest arrival of the period was on 23 October 2025, 8 hours 19 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 23 October 2025 | 8 hours 19 minutes | Carrier |
| 13 March 2026 | 7 hours 41 minutes | Extreme weather |
| 20 July 2026 | 6 hours 52 minutes | Carrier |
| 23 October 2025 | 6 hours 10 minutes | Carrier |
| 15 June 2026 | 4 hours 37 minutes | Carrier |
Delay causes
Why Alaska runs late on this route
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 18,000 reported delay minutes.
- 37%Late-arriving aircraft
- 34%National Airspace System
- 25%Carrier
- 3%Extreme weather
- 0%Security
37% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 18,000 reported delay minutes here, that single category outweighs weather by 11 to one. The split is drawn from 18,189 reported delay minutes.
34% 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 6,175 minutes out of 18,000, against a national NAS share of 21%.
Cancellations sit at 1.27% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
5.0% 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 50 minutes, which a normal layover absorbs.
The 696 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 runs 79.8% on time across 1,887 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,884 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 Alaska on SJC to SEA
Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 95.5% on time and June 67.5%, a swing of 28 points. If the dates move at all, move them out of June before you think about anything else. 1,860 completed flights over 12 months sit behind that.
Related
Where to go next
- SJC to SEA, every carrier
- Alaska on SEA to SJC, the return leg
- SkyWest Airlines on SJC to SEA88.7%
- Southwest Airlines on SJC to SEA75.6%
- Alaska Airlines network-wide record
- Norman Y. Mineta San Jose International (SJC) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
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.