Carrier route record

ASSEA→LAX

Alaska Airlines · Seattle to Los Angeles

Flights: 3,282
Period: July 2025 to June 2026
Share of route: 44%
Carriers: 6

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

Alaska on SEA to LAX 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 roughly 45 minutes on average. That is a workable record, not a spotless one. That rests on 3,282 flights. The strongest carrier on the route with a full sample, United Airlines, flew 393 at 90.3% on time.

United Airlines is the most reliable of the three carriers covered here at 90.3% on time across 393 flights.

On time

81.0%

Arrivals under 15 minutes late, of 3,247 completed flights

Avg delay

43 min

Across delayed arrivals only, not all flights

Cancelled

1.07%

National rate is 1.81%

Whole route

83.4%

Every carrier on SEA to LAX, 7,428 flights

These figures cover 3,282 flights between July 2025 and June 2026. The median arrival is 5 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 LAX

Alaska flew 3,282 of the 7,428 flights on SEA to LAX, about 44% of it. Its 81.0% on time is 2 points worse than the route as a whole, which runs 83.4%. Ranked by on-time rate it is number five of six carriers on the route, where the range runs from American at 90.9% to Frontier at 78.9%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The three carriers here are closely matched: 6 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on SEA to LAX
Airline	Flights	On time	Avg delay	Cancelled	Grade
American Airlinesthin sample	11	90.9%	149 min	0.00%	A+
United Airlines	393	90.3%	98 min	0.00%	A+
SkyWest Airlines	1,241	86.3%	109 min	0.64%	A+
Delta Air Lines	2,225	84.5%	59 min	0.67%	B+
Alaska Airlines (this page)	3,282	81.0%	43 min	1.07%	B
Frontier Airlinesthin sample	276	78.9%	60 min	3.62%	B−

No carrier stands out. United tops the table at 90.3%, 6 points clear of the bottom, which is inside the range this kind of sample moves year to year.

Flight by flight

Alaska flight numbers on SEA to LAX

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 6 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am531 flights89.0%
8am–11am537 flights86.7%
11am–2pm444 flights80.6%
2pm–5pm509 flights80.9%
5pm–8pm714 flights79.1%
8pm–5am547 flights70.7%

Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 89.0% of the time, against 70.7% for the overnight 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 5pm–8pm window is the busiest, with 714 flights scheduled in it.

Across the year

Alaska on SEA to LAX through the year

Darker means more delays. Figures are on-time percentages.April best, December worst

December is the weak month at 70.1% on time, against 89.3% in April. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. July was the busiest month here, with 306 flights.

Across the week, Wednesday is the strongest day at 85.2% on time and Sunday the weakest at 76.7%. 9 points is a smaller lever than departure hour, but it is free.

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 26,000 reported delay minutes.

Late-arriving aircraft
40%
Carrier
40%
National Airspace System
19%
Extreme weather
2%

40% 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 26,000 reported delay minutes here, that single category outweighs weather by 25 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 26,419 reported delay minutes.

The largest share of delay minutes, 40%, 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 10,000 of the 26,000 delay minutes reported here.

Cancellations sit at 1.07% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 3.4% 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 954 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 85.2% on time across 3,279 flights, 4 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 4 points of difference.

The sample behind these figures is 3,282 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 LAX

Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 89.3% on time and December 70.1%, a swing of 19 points. If the dates move at all, move them out of December before you think about anything else. 3,247 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures