Carrier route record

F9SAT→DEN

Frontier Airlines · San Antonio to Denver

Flights: 370
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 SAT to DEN 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 an hour and a half on average. That is a workable record, not a spotless one. That rests on 370 flights. The strongest carrier on the route with a full sample, United Airlines, flew 1,207 at 81.6% on time.

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

On time

79.6%

Arrivals under 15 minutes late, of 367 completed flights

Avg delay

90 min

Across delayed arrivals only, not all flights

Cancelled

0.54%

National rate is 1.81%

Whole route

81.0%

Every carrier on SAT to DEN, 3,027 flights

These figures cover 370 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 SAT to DEN

Frontier flew 370 of the 3,027 flights on SAT to DEN, about 12% of it. Its 79.6% on time is about level with the route as a whole at 81.0%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from SkyWest at 88.9% to Frontier at 79.6%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

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 SAT to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
SkyWest Airlinesthin sample	18	88.9%	169 min	0.00%	A+
United Airlines	1,207	81.6%	78 min	0.58%	B+
Southwest Airlines	1,432	80.8%	53 min	0.28%	B+
Frontier Airlines (this page)	370	79.6%	90 min	0.54%	B+

No carrier stands out. United tops the table at 81.6%, about a point clear of the bottom, which is inside the range this kind of sample moves year to year.

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 28 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am71 flights87.1%
8am–11am31 flights90.3%
11am–2pm35 flights85.7%
2pm–5pm52 flights86.5%
5pm–8pm32 flights62.5%
8pm–5am149 flights73.5%

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

The 5pm–8pm window is where this operation falls apart: 62.5% on time, against 90.3% for the 8am–11am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8pm–5am window is the busiest, with 149 flights scheduled in it.

Across the year

Frontier on SAT to DEN through the year

Jul–Sep 202563 flights69.4%
Oct–Dec 2025113 flights85.0%
Jan–Mar 2026104 flights82.5%
Apr–Jun 202690 flights76.4%

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 79.6% on time across 370 flights.

Frontier on SAT to DEN did not run the same all year. Its best quarter was Oct–Dec 2025 at 85.0% on time and its weakest Jul–Sep 2025 at 69.4%, a swing of 16 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, Friday is the strongest day at 91.4% on time and Tuesday the weakest at 72.5%. 19 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 6,762 reported delay minutes.

Late-arriving aircraft
42%
Carrier
36%
National Airspace System
22%
Extreme weather
0%

42% 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 6,762 reported delay minutes here, that single category outweighs weather by 42 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 6,762 reported delay minutes.

The largest share of delay minutes, 36%, 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 2,427 of the 6,762 delay minutes reported here.

Cancellations are rare at 0.54%, 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

7.9% 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 an hour and a half, 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 81.4% on time across 372 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. 370 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 SAT to DEN

Put together: treat all of this as provisional. 370 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. 367 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