Carrier route record

WNSJC→SLC

Southwest Airlines · San Jose to Salt Lake City

Flights: 208
Period: September 2025 to August 2026
Share of route: 12%
Carriers: 3

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

Southwest on SJC to SLC lands a B+, about a point better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 208 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 662 at 94.1% on time.

The US average over the same twelve months is 77.3%, so there is little to separate Southwest on SJC to SLC from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

78.7%

Arrivals under 15 minutes late, of 207 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

0.48%

National rate is 1.89%

Whole route

91.9%

Every carrier on SJC to SLC, 1,794 flights

These figures cover 208 flights between September 2025 and August 2026. The median arrival is 3 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.

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Carrier by carrier

Southwest against every carrier on SJC to SLC

Southwest flew 208 of the 1,794 flights on SJC to SLC, about 12% of it. Its 78.7% on time is 13 points worse than the route as a whole, which runs 91.9%. Ranked by on-time rate it is last of three carriers on the route, where the range runs from SkyWest at 94.1% to Southwest at 78.7%.

The two carriers here are closely matched: about a point 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	662	94.1%	86 min	0.15%	A+
Delta Air Lines	924	93.2%	86 min	0.54%	A+
Southwest Airlines (this page)thin sample	208	78.7%	56 min	0.48%	B+

No carrier stands out. SkyWest tops the table at 94.1%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.

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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 23 points, against about a point between the best and worst carrier.

5am–8am—
8am–11am62 flights87.1%
11am–2pm41 flights85.0%
2pm–5pm81 flights64.2%
5pm–8pm24 flights—
8pm–5am—

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

Book the morning departure. Flights leaving between 8am–11am arrive on time 87.1% of the time, against 64.2% for the afternoon window. That is 23 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 81 flights scheduled in it.

Across the year

Southwest on SJC to SLC through the year

Jul–Sep 202521 flights—
Oct–Dec 202554 flights81.1%
Jan–Mar 202645 flights84.4%
Apr–Jun 202652 flights73.1%
Jul–Sep 202636 flights66.7%

Scale runs 60% to 90%. 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 78.7% on time across 208 flights.

Southwest on SJC to SLC did not run the same all year. Its best quarter was Jan–Mar 2026 at 84.4% on time and its weakest Jul–Sep 2026 at 66.7%, a swing of 18 points on roughly 52 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, Monday is the strongest day at 82.6% on time and Friday the weakest at 72.3%, a spread of 10 points.

Arrival by arrival

How late Southwest on SJC to SLC runs when it is late

The 44 late arrivals split 20 under half an hour, 10 between 30 and 60 minutes, and 14 an hour or more.

15+ min early26 flights12.6%
Within 15 min137 flights66.2%
15–29 min late20 flights9.7%
30–59 min late10 flights4.8%
1–2 hours late10 flights4.8%
2+ hours late4 flights1.9%

Scale runs 0% to 100%.

Share of 207 completed flights by arrival against schedule.

A late pushback is often recovered here: of 61 departures that left 15 minutes late or more, 19 still arrived on time. Only 2 left on time and still arrived late.

The worst days

Worst days for Southwest on SJC to SLC

The latest arrival of the period was on 15 March 2026, 4 hours 34 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on three of the five worst days.

The latest arrivals of Southwest on SJC to SLC in the period
Date	Arrived late by	Largest filed cause
15 March 2026	4 hours 34 minutes	Carrier
10 July 2026	3 hours 49 minutes	Carrier
22 November 2025	3 hours 24 minutes	Carrier
13 February 2026	2 hours	Late-arriving aircraft
13 August 2026	1 hour 54 minutes	National Airspace System

Delay causes

Why Southwest runs late on this route

Late-arriving aircraft accounts for 48% of the 2,465 delay minutes carriers reported here, and the remaining four split what is left.

Late-arriving aircraft
48%
Carrier
42%
National Airspace System
9%

48% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 2,465 reported delay minutes here, that single category outweighs weather by 48 to one. The split is drawn from 2,465 reported delay minutes.

The largest share of delay minutes, 42%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 1,046 of the 2,465 delay minutes reported here.

Cancellations are rare at 0.48%, below the national 1.89% 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

6.8% 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 about an hour, which a normal layover absorbs.

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.

The return leg is a different operation and performs like one: it runs 74.3% on time across 208 flights, 4 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 4 points of difference.

One caution: this is a thin sample. 208 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. 208 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 78.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 207 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