Carrier route record

F9DEN→SAT

Frontier Airlines · Denver to San Antonio

Flights: 372
Period: July 2025 to June 2026
Share of route: 12%
Carriers: 4

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

Frontier on DEN to SAT lands a B+, 4 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 372 flights. The strongest carrier on the route with a full sample, United Airlines, flew 1,205 at 81.9% on time.

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

On time

81.4%

Arrivals under 15 minutes late, of 370 completed flights

Avg delay

60 min

Across delayed arrivals only, not all flights

Cancelled

0.27%

National rate is 1.81%

Whole route

76.5%

Every carrier on DEN to SAT, 3,030 flights

These figures cover 372 flights between July 2025 and June 2026. The median arrival is 11 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 SAT

Frontier flew 372 of the 3,030 flights on DEN to SAT, about 12% of it. Its 81.4% on time is 5 points better than the route as a whole, which runs 76.5%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from United at 81.9% to Southwest at 70.7%. 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 81.9% of the time; Southwest Airlines manages 70.7%. Sample sizes sit next to every figure, because a two-point gap across 1,434 flights means less than a ten-point one.

On-time performance by carrier on DEN to SAT
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	1,205	81.9%	63 min	0.25%	B+
Frontier Airlines (this page)	372	81.4%	60 min	0.27%	B+
SkyWest Airlinesthin sample	19	78.9%	192 min	0.00%	B+
Southwest Airlines	1,434	70.7%	52 min	0.21%	C+

United leads Southwest by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Departure window

When Frontier 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 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am41 flights87.8%
8am–11am31 flights83.9%
11am–2pm54 flights85.2%
2pm–5pm175 flights81.0%
5pm–8pm—
8pm–5am71 flights74.3%

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

Book the early departure. Flights leaving between 5am–8am arrive on time 87.8% of the time, against 74.3% for the overnight 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 175 flights scheduled in it.

Across the year

Frontier on DEN to SAT through the year

Jul–Sep 202564 flights79.4%
Oct–Dec 2025114 flights86.8%
Jan–Mar 2026104 flights74.8%
Apr–Jun 202690 flights83.3%

Scale runs 65% 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 81.4% on time across 372 flights.

Frontier on DEN to SAT did not run the same all year. Its best quarter was Oct–Dec 2025 at 86.8% on time and its weakest Jan–Mar 2026 at 74.8%, a swing of 12 points on roughly 93 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 89.7% on time and Monday the weakest at 71.2%. 19 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Frontier runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 50% of the 4,127 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
30%
National Airspace System
14%
Extreme weather
6%

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 4,127 reported delay minutes here, that single category outweighs weather by 8 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 4,127 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 87.8% on time here.

Cancellations are rare at 0.27%, 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

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 794 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 79.6% on time across 370 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. 372 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 SAT

Put together: treat all of this as provisional. 372 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 81.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 370 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