Route reliability record
DEN→SAT
Denver to San Antonio
- Flights
- 3,067
- Period
- September 2025 to August 2026
- Distance
- 794 mi
- Carriers
- 4
This route lands a B+, level with the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 3,067 DEN to SAT flights, of which United Airlines flew 1,196 at 83.6% on time.
Best time to fly DEN to SAT: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 90.7% of the time and Wednesday flights 83.1%, against 76.8% for the route overall.
United Airlines is the most reliable of the three carriers covered here at 83.6% on time across 1,196 flights.
Key figures
On time
76.8%
Arrivals under 15 minutes late, of 3,056 completed flights
Avg delay
61 min
Across delayed arrivals only, not all flights
Cancelled
0.26%
National rate is 1.89%
Best carrier
United
83.6% on time across 1,196 flights
These figures cover 3,067 flights between September 2025 and August 2026. The median arrival is 5 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.
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Carrier by carrier
Which airline is most reliable on DEN to SAT
The choice of carrier is not cosmetic here. United Airlines arrives on time 83.6% of the time; Southwest Airlines manages 70.3%. Sample sizes sit next to every figure, because a two-point gap across 1,435 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,196 | 83.6% | 72 min | 0.17% | B+ |
| Frontier Airlines | 396 | 81.0% | 62 min | 0.25% | B+ |
| Southwest Airlines | 1,435 | 70.3% | 55 min | 0.28% | C+ |
| SkyWest Airlinesthin sample | 40 | 64.1% | 88 min | 2.50% | D |
The spread between United 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.
Flight by flight
Flights on DEN to SAT
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Denver to San Antonio
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. DEN → SATDenver to San Antonio | United Airlines | 83.5% | 83.6% | 0.17% | 8am–11am, Sat | UA 2625 09:35 |
| 2. DEN → SATDenver to San Antonio | Frontier Airlines | 80.8% | 81.0% | 0.25% | 5am–8am, Thu | — |
| 3. DEN → SATDenver to San Antonio | Southwest Airlines | 70.1% | 70.3% | 0.28% | 8am–11am, Wed | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 30 points, against 13 points between the best and worst carrier.
- 5am–8am113 flights85.6%
- 8am–11am689 flights90.7%
- 11am–2pm736 flights83.8%
- 2pm–5pm534 flights71.3%
- 5pm–8pm673 flights65.2%
- 8pm–5am322 flights60.8%
Scale runs 50% to 95%.
The 8pm–5am window is where this operation falls apart: 60.8% on time, against 90.7% 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 11am–2pm window is the busiest, with 736 flights scheduled in it.
Explore
Filter DEN to SAT by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On DEN to SAT, the best departure window is 8am–11am at 90.7% on time and the worst is 8pm–5am at 60.8%, a wide gap of 29.9 points. All US flights leaving 8am–11am ran 83.9%.
- 5–8am85.6%
- 8–11am90.7%
- 11am–2pm83.8%
- 2–5pm71.3%
- 5–8pm65.2%
- 8pm–5am60.8%
best all US flightsScale 50% to 95%.
Across the year
When delays peak on this route
This route's year swings by 25 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
June is the worst month at 62.1% on time, 25 points below November, the best at 87.6%. 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 299 flights.
Across the week, Wednesday is the strongest day at 83.1% on time and Friday the weakest at 71.1%, a spread of 12 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 58% of the 43,000 delay minutes carriers reported here, and the remaining four split what is left.
- 58%Late-arriving aircraft
- 29%Carrier
- 11%National Airspace System
- 2%Extreme weather
- 0%Security
58% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 43,000 reported delay minutes here, that single category outweighs weather by 33 to one. The split is drawn from 43,333 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 90.7% on time here.
Cancellations are rare at 0.26%, below the national 1.89% 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 actually costs
7.6% of arrivals land an hour or more late, close to the national 8.3%, so 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.
The return leg is a different operation and performs like one: it runs 82.1% on time across 3,063 flights, 5 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 5 points of difference.
The sample behind these figures is 3,067 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in SAT after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 87.6% on time and June 62.1%, a swing of 25 points. If the dates move at all, move them out of June before you think about anything else. 3,056 completed flights over 12 months sit behind that.
Common questions
DEN to SAT questions
How often is DEN to SAT delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.2% of the 3,067 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on DEN to SAT?
United Airlines leads at 83.6% on time across 1,196 flights. Southwest Airlines is at the other end on 70.3%, a gap of 13 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on DEN to SAT?
The 8am–11am departure window is the strongest at 90.7% on time. The 8pm–5am window is the weakest at 60.8%, 30 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are June delays on DEN to SAT?
June is the weakest month at 62.1% on time, compared with 87.6% in November. Across the year that is 25 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SAT to DEN — the return legseparate record
- Denver International (DEN) delay statistics
- San Antonio International (SAT) delay statistics
- United Airlines on DEN to SAT83.6%
- Frontier Airlines on DEN to SAT81.0%
- Southwest Airlines on DEN to SAT70.3%
- DEN to PHX, a related route75.6%
- DFW to SAT, a related route67.8%
- DEN to SLC, a related route78.2%
- United Airlines on-time record83.6%
- Frontier Airlines on-time record81.0%
- Southwest Airlines on-time record70.3%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
Direction matters. DEN to SAT and SAT to DEN are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.