Carrier route record

WNSJC→SLC

Southwest Airlines · San Jose to Salt Lake City

Flights: 224
Period: July 2025 to June 2026
Share of route: 12%
Carriers: 3

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

Southwest on SJC to SLC lands a B+, 6 points better than the national rate of 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by roughly 55 minutes on average. That is a workable record, not a spotless one. That rests on 224 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 692 at 94.9% on time.

Set against the rest of the country, Southwest's SJC to SLC record is 6 points better than the US average of 77.6%. That gap is worth roughly 58 fewer late arrivals for every thousand flights.

On time

83.4%

Arrivals under 15 minutes late, of 223 completed flights

Avg delay

53 min

Across delayed arrivals only, not all flights

Cancelled

0.45%

National rate is 1.81%

Whole route

92.2%

Every carrier on SJC to SLC, 1,808 flights

These figures cover 224 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

Southwest against every carrier on SJC to SLC

Southwest flew 224 of the 1,808 flights on SJC to SLC, about 12% of it. Its 83.4% on time is 9 points worse than the route as a whole, which runs 92.2%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 94.9% to Southwest at 83.4%.

The two carriers here are closely matched: 3 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 SJC to SLC
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlines	692	94.9%	85 min	0.14%	A+
Delta Air Lines	892	92.3%	100 min	0.67%	A+
Southwest Airlines (this page)thin sample	224	83.4%	53 min	0.45%	B+

No carrier stands out. SkyWest tops the table at 94.9%, 3 points clear of the bottom, which is inside the range this kind of sample moves year to year.

Departure window

When Southwest runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 14 points, against 3 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am—
8am–11am66 flights87.9%
11am–2pm52 flights86.3%
2pm–5pm82 flights74.4%
5pm–8pm24 flights—
8pm–5am—

Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.

Book the morning departure. Flights leaving between 8am–11am arrive on time 87.9% of the time, against 74.4% for the afternoon window. That is 14 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 82 flights scheduled in it.

Across the year

Southwest on SJC to SLC through the year

Jul–Sep 202573 flights91.8%
Oct–Dec 202554 flights81.1%
Jan–Mar 202645 flights84.4%
Apr–Jun 202652 flights73.1%

Scale runs 65% to 95%. 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 83.4% on time across 224 flights.

Southwest on SJC to SLC did not run the same all year. Its best quarter was Jul–Sep 2025 at 91.8% on time and its weakest Apr–Jun 2026 at 73.1%, a swing of 19 points on roughly 56 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Across the week, Thursday is the strongest day at 86.0% on time and Sunday the weakest at 72.9%. 13 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Southwest runs late on this route

One category carries most of the weight here. Carrier accounts for 51% of the 1,949 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
51%
Late-arriving aircraft
41%
National Airspace System
9%

41% 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 1,949 reported delay minutes here, that single category outweighs weather by 41 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 1,949 reported delay minutes.

The largest share of delay minutes, 51%, 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 985 of the 1,949 delay minutes reported here.

Cancellations are rare at 0.45%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 4.9% 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 584 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 77.9% on time across 224 flights, 6 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 6 points of difference.

One caution: this is a thin sample. 224 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 Southwest on SJC to SLC

Put together: treat all of this as provisional. 224 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 83.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 223 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