Carrier route record

ASSFO→SEA

Alaska Airlines · San Francisco to Seattle

Flights: 2,729
Period: September 2025 to August 2026
Share of route: 40%
Carriers: 5

Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Alaska Airlines.

Alaska on SFO to SEA sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.3%. The late ones land roughly 55 minutes behind schedule. That rests on 2,729 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 986 at 79.5% on time.

Delta Air Lines is the most reliable of the three carriers covered here at 79.5% on time across 986 flights.

On time

68.8%

Arrivals under 15 minutes late, of 2,690 completed flights

Avg delay

54 min

Across delayed arrivals only, not all flights

Cancelled

1.28%

National rate is 1.89%

Whole route

72.3%

Every carrier on SFO to SEA, 6,821 flights

These figures cover 2,729 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

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Carrier by carrier

Alaska against every carrier on SFO to SEA

Alaska flew 2,729 of the 6,821 flights on SFO to SEA, about 40% of it. Its 68.8% on time is 4 points worse than the route as a whole, which runs 72.3%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from Southwest at 100.0% to SkyWest at 68.8%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 79.5% of the time; SkyWest Airlines manages 68.8%. Sample sizes sit next to every figure, because a two-point gap across 1,040 flights means less than a ten-point one.

On-time performance by carrier on SFO to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Southwest Airlinesthin sample	3	100.0%	—	0.00%	A+
Delta Air Lines	986	79.5%	70 min	1.83%	B
United Airlines	2,063	75.1%	57 min	0.44%	B+
Alaska Airlines (this page)	2,729	68.8%	54 min	1.28%	C
SkyWest Airlines	1,040	68.8%	50 min	1.15%	C

Delta leads SkyWest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Flight by flight

Alaska flight numbers on SFO 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 33 points, against 11 points between the best and worst carrier.

5am–8am402 flights90.2%
8am–11am525 flights57.6%
11am–2pm398 flights65.9%
2pm–5pm533 flights69.4%
5pm–8pm575 flights69.5%
8pm–5am296 flights61.3%

Scale runs 50% to 95%.

Book the early departure. Flights leaving between 5am–8am arrive on time 90.2% of the time, against 57.6% for the morning window. That is 33 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 575 flights scheduled in it.

Across the year

Alaska on SFO to SEA through the year

Darker means more delays. Figures are on-time percentages.February best, August worst

August is the worst month at 54.6% on time, 36 points below February, the best at 90.2%. 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 283 flights.

Across the week, Tuesday is the strongest day at 75.9% on time and Thursday the weakest at 62.5%, a spread of 13 points.

Arrival by arrival

How late Alaska on SFO to SEA runs when it is late

The 838 late arrivals split 311 under half an hour, 328 between 30 and 60 minutes, and 199 an hour or more.

15+ min early566 flights21.0%
Within 15 min1,286 flights47.8%
15–29 min late311 flights11.6%
30–59 min late328 flights12.2%
1–2 hours late133 flights4.9%
2+ hours late66 flights2.5%

Scale runs 0% to 100%.

Share of 2,690 completed flights by arrival against schedule.

122 of 735 late departures made up the time and arrived on time, 17% of them. In the other direction, 225 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 SFO to SEA

The latest arrival of the period was on 2 January 2026, 9 hours 6 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. On three of the five worst days the largest share was filed as carrier-caused (crew, maintenance, fuelling, baggage).

The latest arrivals of Alaska on SFO to SEA in the period
Date	Arrived late by	Largest filed cause
2 January 2026	9 hours 6 minutes	Late-arriving aircraft
2 July 2026	9 hours 2 minutes	Carrier
22 June 2026	8 hours 34 minutes	Late-arriving aircraft
25 April 2026	8 hours 26 minutes	Carrier
8 December 2025	7 hours 54 minutes	Carrier

Delay causes

Why Alaska runs late on this route

Late-arriving aircraft accounts for 53% of the 45,000 delay minutes carriers reported here, and the remaining four split what is left.

Late-arriving aircraft
53%
Carrier
24%
National Airspace System
23%
Extreme weather
0%

53% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 45,000 reported delay minutes here, that single category outweighs weather by 53 to one. The split is drawn from 45,099 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 90.2% on time here.

Cancellations sit at 1.28% against a national 1.89%, which is ordinary. Diversions add another 0.15%.

Connections and stage length

What a delay here costs

7.4% 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 55 minutes, which a normal layover absorbs.

The 679 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 56.0% on time across 2,727 flights, 13 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 13 points of difference.

The sample behind these figures is 2,729 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 SFO to SEA

Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 90.2% on time and August 54.6%, a swing of 36 points. If the dates move at all, move them out of August before you think about anything else. 2,690 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated 22 October 2026; recomputed monthly. How this data is collected.

Key figures