Carrier route record

WNSLC→SAN

Southwest Airlines · Salt Lake City to San Diego

Flights: 408
Period: July 2025 to June 2026
Share of route: 14%
Carriers: 5

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

Southwest on SLC to SAN sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land roughly 45 minutes behind schedule. That rests on 408 flights. The strongest carrier on the route with a full sample, SkyWest Airlines, flew 685 at 85.9% on time.

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

On time

75.8%

Arrivals under 15 minutes late, of 405 completed flights

Avg delay

47 min

Across delayed arrivals only, not all flights

Cancelled

0.25%

National rate is 1.81%

Whole route

83.2%

Every carrier on SLC to SAN, 2,958 flights

These figures cover 408 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.

Carrier by carrier

Southwest against every carrier on SLC to SAN

Southwest flew 408 of the 2,958 flights on SLC to SAN, about 14% of it. Its 75.8% on time is 7 points worse than the route as a whole, which runs 83.2%. Ranked by on-time rate it is last of five carriers on the route, where the range runs from Alaska at 100.0% to Southwest at 75.8%. Two of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The two carriers here are closely matched: 2 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 SLC to SAN
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlinesthin sample	1	100.0%	—	0.00%	A+
SkyWest Airlines	685	85.9%	58 min	1.02%	A
Frontier Airlinesthin sample	133	84.6%	50 min	2.26%	B
Delta Air Lines	1,731	83.8%	55 min	0.81%	B+
Southwest Airlines (this page)	408	75.8%	47 min	0.25%	B+

No carrier stands out. SkyWest tops the table at 85.9%, 2 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 33 points, against 2 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am30 flights100.0%
8am–11am28 flights—
11am–2pm126 flights75.4%
2pm–5pm132 flights74.6%
5pm–8pm92 flights67.0%
8pm–5am—

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

Book the early departure. Flights leaving between 5am–8am arrive on time 100.0% of the time, against 67.0% for the evening window. That is 33 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 132 flights scheduled in it.

Across the year

Southwest on SLC to SAN through the year

Darker means more delays. Figures are on-time percentages.March best, June worst

June is the worst month at 53.3% on time, 37 points below March, the best at 90.0%. 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. December was the busiest month here, with 42 flights.

Across the week, Tuesday is the strongest day at 83.9% on time and Sunday the weakest at 69.2%. 15 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. Late-arriving aircraft accounts for 50% of the 4,613 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
50%
Carrier
32%
National Airspace System
18%
Extreme weather
1%

50% 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 4,613 reported delay minutes here, that single category outweighs weather by 49 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 4,613 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 100.0% on time here.

Cancellations are rare at 0.25%, 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 626 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 76.6% on time across 408 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 408 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 SLC to SAN

Put together: treat all of this as provisional. 408 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 75.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 405 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