Carrier route record

ASSEA→SLC

Alaska Airlines · Seattle to Salt Lake City

Flights: 1,372
Period: July 2025 to June 2026
Share of route: 33%
Carriers: 4

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

Alaska on SEA to SLC lands a B, 2 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 40 minutes on average. That is a workable record, not a spotless one. That rests on 1,372 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,219 at 87.0% on time.

The US average over the same twelve months is 77.6%, so there is little to separate Alaska on SEA to SLC from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

79.6%

Arrivals under 15 minutes late, of 1,347 completed flights

Avg delay

41 min

Across delayed arrivals only, not all flights

Cancelled

1.68%

National rate is 1.81%

Whole route

83.6%

Every carrier on SEA to SLC, 4,107 flights

These figures cover 1,372 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 SLC

Alaska flew 1,372 of the 4,107 flights on SEA to SLC, about 33% of it. Its 79.6% on time is 4 points worse than the route as a whole, which runs 83.6%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from Delta at 87.0% to Frontier at 72.6%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The two 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 SLC
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	2,219	87.0%	58 min	0.54%	A+
SkyWest Airlines	418	81.3%	49 min	0.00%	B+
Alaska Airlines (this page)	1,372	79.6%	41 min	1.68%	B
Frontier Airlinesthin sample	98	72.6%	55 min	3.06%	C−

No carrier stands out. Delta tops the table at 87.0%, 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 SLC

AS 73311:3866.2% · 271 flights

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

5am–8am180 flights93.2%
8am–11am217 flights82.1%
11am–2pm355 flights70.7%
2pm–5pm378 flights80.7%
5pm–8pm128 flights76.4%
8pm–5am114 flights81.2%

Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.

The weak window here is the middle of the day, not the evening: 11am–2pm runs 70.7% on time against 93.2% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 2pm–5pm window is the busiest, with 378 flights scheduled in it.

Across the year

Alaska on SEA to SLC through the year

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

July is the worst month at 62.2% on time, 34 points below April, the best at 96.1%. 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 135 flights.

Across the week, Wednesday is the strongest day at 84.2% on time and Thursday the weakest at 76.7%. 8 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 46% of the 11,000 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.

Late-arriving aircraft
46%
Carrier
39%
National Airspace System
15%
Security
0%

46% 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 11,000 reported delay minutes here, that single category outweighs weather by 46 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 11,259 reported delay minutes.

The largest share of delay minutes, 39%, 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 4,441 of the 11,000 delay minutes reported here.

Cancellations sit at 1.68% against a national 1.81%, which is ordinary. Diversions add another 0.15%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 3.6% 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 689 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 76.7% on time across 1,369 flights, within 3 points 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 1,372 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 SLC

Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 96.1% on time and July 62.2%, a swing of 34 points. If the dates move at all, move them out of July before you think about anything else. 1,347 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