Carrier route record

F9DEN→SAN

Frontier Airlines · Denver to San Diego

Flights: 703
Period: July 2025 to June 2026
Share of route: 12%
Carriers: 5

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

Frontier on DEN to SAN lands a B+, 2 points better than the national rate of 77.6%. About one flight in five 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 703 flights. The strongest carrier on the route with a full sample, Alaska Airlines, flew 433 at 82.9% on time.

Alaska Airlines is the most reliable of the three carriers covered here at 82.9% on time across 433 flights.

On time

79.6%

Arrivals under 15 minutes late, of 696 completed flights

Avg delay

63 min

Across delayed arrivals only, not all flights

Cancelled

0.85%

National rate is 1.81%

Whole route

75.6%

Every carrier on DEN to SAN, 5,949 flights

These figures cover 703 flights between July 2025 and June 2026. The median arrival is 9 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

Frontier against every carrier on DEN to SAN

Frontier flew 703 of the 5,949 flights on DEN to SAN, about 12% of it. Its 79.6% on time is 4 points better than the route as a whole, which runs 75.6%. Ranked by on-time rate it is number three 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. Alaska Airlines arrives on time 82.9% 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	433	82.9%	56 min	1.15%	B
United Airlines	2,081	79.8%	59 min	0.48%	B+
Frontier Airlines (this page)	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+

The spread between Alaska and Southwest is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.

Departure window

When Frontier runs best on this route

Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 703 flights.

5am–8am87 flights83.5%
8am–11am128 flights85.9%
11am–2pm9 flights—
2pm–5pm9 flights—
5pm–8pm107 flights78.1%
8pm–5am363 flights76.4%

Scale runs 70% to 90%. Rows with fewer than 30 flights show a dash.

Book the morning departure. Flights leaving between 8am–11am arrive on time 85.9% of the time, against 76.4% for the overnight window. That is 10 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 363 flights scheduled in it.

Across the year

Frontier on DEN to SAN through the year

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

July is the worst month at 65.6% on time, 21 points below March, the best at 86.4%. 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. March was the busiest month here, with 68 flights.

Across the week, Tuesday is the strongest day at 84.1% on time and Sunday the weakest at 74.3%. 10 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Frontier runs late on this route

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 9,004 reported delay minutes.

Carrier
38%
National Airspace System
32%
Late-arriving aircraft
28%
Extreme weather
1%

The largest share of delay minutes, 38%, 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 3,465 of the 9,004 delay minutes reported here. The split is drawn from 9,004 reported delay minutes.

The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 85.9% on time here.

Cancellations are rare at 0.85%, 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

6.8% 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 81.6% on time across 704 flights, within 2 points 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. 703 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 Frontier on DEN to SAN

Put together: treat all of this as provisional. 703 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 79.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 696 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