Carrier route record
ASSEA→SJC
Alaska Airlines · Seattle to San Jose
- Flights
- 1,877
- Period
- July 2025 to June 2026
- Share of route
- 43%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Alaska Airlines.
Alaska on SEA to SJC lands a B, 3 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about 45 minutes on average. That is a workable record, not a spotless one. That rests on 1,877 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 1,562 at 88.0% on time.
The US average over the same twelve months is 77.6%, so there is little to separate Alaska on SEA to SJC from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.6%
Arrivals under 15 minutes late, of 1,847 completed flights
Avg delay
45 min
Across delayed arrivals only, not all flights
Cancelled
1.55%
National rate is 1.81%
Whole route
81.6%
Every carrier on SEA to SJC, 4,371 flights
These figures cover 1,877 flights between July 2025 and June 2026. The median arrival is 6 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
Alaska against every carrier on SEA to SJC
Alaska flew 1,877 of the 4,371 flights on SEA to SJC, about 43% of it. Its 80.6% on time is about level with the route as a whole at 81.6%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from American at 100.0% to Southwest at 72.6%. Two 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 88.0% of the time; Southwest Airlines manages 72.6%. Sample sizes sit next to every figure, because a two-point gap across 927 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlinesthin sample | 4 | 100.0% | — | 0.00% | A+ |
| United Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlines | 1,562 | 88.0% | 61 min | 0.19% | A+ |
| Alaska Airlines (this page) | 1,877 | 80.6% | 45 min | 1.55% | B |
| Southwest Airlines | 927 | 72.6% | 45 min | 0.32% | C+ |
The spread between SkyWest and Southwest is 15 points, wide enough that it should decide the booking. On a hundred trips that is 15 more arrivals inside the on-time window.
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 20 points, against 15 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am260 flights93.2%
- 8am–11am247 flights82.8%
- 11am–2pm385 flights75.8%
- 2pm–5pm413 flights81.2%
- 5pm–8pm391 flights78.1%
- 8pm–5am181 flights73.7%
Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 93.2% of the time, against 73.7% for the overnight window. That is 20 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 413 flights scheduled in it.
Across the year
Alaska on SEA to SJC through the year
July is the worst month at 66.3% on time, 23 points below April, the best at 89.3%. 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 187 flights.
Across the week, Wednesday is the strongest day at 86.9% on time and Friday the weakest at 74.7%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Alaska runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 50% 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.
- 50%Late-arriving aircraft
- 38%Carrier
- 11%National Airspace System
- 1%Security
- 0%Extreme weather
50% 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 50 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 15,968 reported delay minutes.
The largest share of delay minutes, 38%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 6,018 of the 16,000 delay minutes reported here.
Cancellations sit at 1.55% against a national 1.81%, which is ordinary. Diversions add another 0.05%.
Connections and stage length
What a delay here costs
Badly late arrivals are rare here: only 4.3% 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 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. 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 runs 82.0% on time across 1,874 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 1,877 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 SEA to SJC
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 89.3% on time and July 66.3%, a swing of 23 points. If the dates move at all, move them out of July before you think about anything else. 1,847 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to SJC, every carrier
- Alaska on SJC to SEA, the return leg
- SkyWest Airlines on SEA to SJC88.0%
- Southwest Airlines on SEA to SJC72.6%
- Alaska Airlines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Norman Y. Mineta San Jose International (SJC) 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.