Carrier route record

OOSLC→SEA

SkyWest Airlines · Salt Lake City to Seattle

Flights: 419
Period: July 2025 to June 2026
Share of route: 10%
Carriers: 4

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

SkyWest on SLC to SEA lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 419 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,222 at 83.3% on time.

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

On time

77.3%

Arrivals under 15 minutes late, of 415 completed flights

Avg delay

73 min

Across delayed arrivals only, not all flights

Cancelled

0.00%

National rate is 1.81%

Whole route

80.2%

Every carrier on SLC to SEA, 4,108 flights

These figures cover 419 flights between July 2025 and June 2026. The median arrival is 4 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

SkyWest against every carrier on SLC to SEA

SkyWest flew 419 of the 4,108 flights on SLC to SEA, about 10% of it. Its 77.3% on time is 3 points worse than the route as a whole, which runs 80.2%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from Delta at 83.3% to Frontier at 69.5%. 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 83.3% of the time; Alaska Airlines manages 76.7%. Sample sizes sit next to every figure, because a two-point gap across 1,369 flights means less than a ten-point one.

On-time performance by carrier on SLC to SEA
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines	2,222	83.3%	54 min	0.54%	B+
SkyWest Airlines (this page)	419	77.3%	73 min	0.00%	B+
Alaska Airlines	1,369	76.7%	46 min	1.83%	B
Frontier Airlinesthin sample	98	69.5%	62 min	3.06%	C−

Delta leads Alaska by 7 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Departure window

When SkyWest runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 45 points, against 7 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am259 flights94.5%
8am–11am160 flights49.7%
11am–2pm—
2pm–5pm—
5pm–8pm—
8pm–5am—

Scale runs 40% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 94.5% of the time, against 49.7% for the morning window. That is 45 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 259 flights scheduled in it.

Across the year

SkyWest on SLC to SEA through the year

Jul–Sep 2025184 flights76.0%
Oct–Dec 202596 flights77.4%
Jan–Mar 202620 flights—
Apr–Jun 2026119 flights77.3%

Scale runs 70% to 85%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 77.3% on time across 419 flights.

Quarter by quarter SkyWest on SLC to SEA held fairly steady: 76.0% in Jul–Sep 2025, 77.4% in Oct–Dec 2025 and 77.3% in Apr–Jun 2026. A spread of about a point is about what a sample of this size moves on its own, so the annual figure is a fair summary.

Across the week, Wednesday is the strongest day at 84.7% on time and Friday the weakest at 72.9%. 12 points is a smaller lever than departure hour, but it is free.

Delay causes

Why SkyWest runs late on this route

One category carries most of the weight here. Carrier accounts for 61% of the 6,899 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.

Carrier
61%
Late-arriving aircraft
21%
National Airspace System
10%
Extreme weather
7%

The largest share of delay minutes, 61%, 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 4,199 of the 6,899 delay minutes reported here. The split is drawn from 6,899 reported delay minutes.

Cancellations are rare at 0.00%, below the national 1.81% and low enough to earn the plus on the grade. Almost no flights are called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

6.3% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.

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 is a different operation and performs like one: it runs 81.3% on time across 418 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.

One caution: this is a thin sample. 419 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking SkyWest on SLC to SEA

Put together: treat all of this as provisional. 419 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 77.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 415 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