Carrier route record

ASDEN→SAN

Alaska Airlines · Denver to San Diego

Flights: 433
Period: July 2025 to June 2026
Share of route: 7%
Carriers: 5

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

Alaska on DEN to SAN lands a B, 5 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 about an hour on average. That is a workable record, not a spotless one. That rests on 433 flights. The strongest carrier on the route with a full sample, United Airlines, flew 2,081 at 79.8% on time.

Set against the rest of the country, Alaska's DEN to SAN record is 5 points better than the US average of 77.6%. That gap is worth roughly 53 fewer late arrivals for every thousand flights.

On time

82.9%

Arrivals under 15 minutes late, of 427 completed flights

Avg delay

56 min

Across delayed arrivals only, not all flights

Cancelled

1.15%

National rate is 1.81%

Whole route

75.6%

Every carrier on DEN to SAN, 5,949 flights

These figures cover 433 flights between July 2025 and June 2026. The median arrival is 10 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 DEN to SAN

Alaska flew 433 of the 5,949 flights on DEN to SAN, about 7% of it. Its 82.9% on time is 7 points better than the route as a whole, which runs 75.6%. Ranked by on-time rate it is first of five carriers on the route, where the range runs from Alaska at 82.9% to Southwest 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. United Airlines arrives on time 79.8% of the time; Southwest Airlines manages 69.5%. Sample sizes sit next to every figure, because a two-point gap across 2,389 flights means less than a ten-point one.

On-time performance by carrier on DEN to SAN
Airline	Flights	On time	Avg delay	Cancelled	Grade
Alaska Airlines (this page)	433	82.9%	56 min	1.15%	B
United Airlines	2,081	79.8%	59 min	0.48%	B+
Frontier Airlines	703	79.6%	63 min	0.85%	B+
SkyWest Airlinesthin sample	343	75.0%	40 min	0.87%	B+
Southwest Airlines	2,389	69.5%	55 min	0.63%	C+

United leads Southwest by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

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 19 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am78 flights92.3%
8am–11am—
11am–2pm173 flights88.2%
2pm–5pm21 flights—
5pm–8pm161 flights73.4%
8pm–5am—

Scale runs 65% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 92.3% of the time, against 73.4% for the evening window. That is 19 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 173 flights scheduled in it.

Across the year

Alaska on DEN to SAN through the year

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

December is the weak month at 67.7% on time, against 95.8% in April. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. March was the busiest month here, with 76 flights.

Across the week, Wednesday is the strongest day at 89.3% on time and Sunday the weakest at 72.3%. 17 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 49% of the 4,073 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
49%
National Airspace System
38%
Carrier
12%
Extreme weather
0%

49% 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 4,073 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 4,073 reported delay minutes.

38% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 1,546 minutes out of 4,073, against a national NAS share of 21%.

Cancellations sit at 1.15% against a national 1.81%, which is ordinary. Diversions add another 0.23%.

Connections and stage length

What a delay here costs

5.4% 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 about an hour, which a normal layover absorbs.

The 853 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 83.4% on time across 433 flights, within half 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. 433 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 Alaska on DEN to SAN

Put together: treat all of this as provisional. 433 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 82.9% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 427 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