Route reliability record
AUS→DEN
Austin to Denver
- Flights
- 5,231
- Period
- June 2025 to May 2026
- Distance
- 775 mi
- Carriers
- 4
This route lands a B+, level with the national rate of 77.4%. Roughly one flight in five arrive 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 5,231 flights, of which Frontier Airlines flew 521 at 85.5% on time.
Frontier Airlines is the most reliable of the four carriers covered here at 85.5% on time across 521 flights.
Key figures
On time
77.9%
Arrivals under 15 minutes late, of 5,175 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.80%
Best carrier
Frontier
85.5% on time across 521 flights
These figures cover 5,231 flights between June 2025 and May 2026. Beyond the headline rate, 8.1% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on AUS to DEN
The choice of carrier is not cosmetic here. Frontier Airlines arrives on time 85.5% of the time; Southwest Airlines manages 73.1%. Sample sizes sit next to every figure, because a two-point gap across 2,347 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlines | 521 | 85.5% | 94 min | 0.58% | A+ |
| SkyWest Airlines | 430 | 83.1% | 76 min | 0.70% | B+ |
| United Airlines | 1,933 | 80.6% | 72 min | 1.35% | B |
| Southwest Airlines | 2,347 | 73.1% | 58 min | 0.47% | C+ |
The spread between Frontier and Southwest is 12 points, wide enough that it should decide the booking. On a hundred trips that is 12 more arrivals inside the on-time window.
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 33 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am995 flights92.4%
- 8am–11am858 flights87.4%
- 11am–2pm1,054 flights87.8%
- 2pm–5pm749 flights69.3%
- 5pm–8pm1,131 flights59.4%
- 8pm–5am444 flights64.8%
Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 59.4% on time, against 92.4% for the 5am–8am 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.
Across the year
When delays peak on this route
This route's year swings by 21 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.
July is the worst month at 64.9% on time, 21 points below January, the best at 85.4%. 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.
Across the week, Tuesday is the strongest day at 82.0% on time and Thursday the weakest at 74.7%. 7 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
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 76,000 reported delay minutes.
- 41%Late-arriving aircraft
- 31%National Airspace System
- 24%Carrier
- 4%Extreme weather
- 0%Security
41% 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 76,000 reported delay minutes here, that single category outweighs weather by 11 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 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 92.4% on time here.
Cancellations are rare at 0.82%, below the national 1.80% 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
8.1% of arrivals land an hour or more late, close to the national 8.2%. 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 are the about an hour kind, which a normal layover absorbs.
The 775 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 76.2% on time across 5,231 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.
The sample behind these figures is 5,231 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.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 85.4% on time and July 64.9%, a swing of 21 points. If the dates move at all, move them out of July before you think about anything else.
Common questions
AUS to DEN questions
How often is AUS to DEN delayed?
Roughly one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.1% of the 5,231 flights in this analysis, against 22.6% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on AUS to DEN?
Frontier Airlines leads at 85.5% on time across 521 flights. Southwest Airlines is at the other end on 73.1%, a gap of 12 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 AUS to DEN?
The 5am–8am departure window is the strongest at 92.4% on time. The 5pm–8pm window is the weakest at 59.4%, 33 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 July delays on AUS to DEN?
July is the weakest month at 64.9% on time, compared with 85.4% in January. Across the year that is 21 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
- DEN to AUS — the return legseparate record
- Austin-Bergstrom International (AUS) delay statistics
- Denver International (DEN) delay statistics
- Frontier Airlines on-time record85.5%
- SkyWest Airlines on-time record83.1%
- United Airlines on-time record80.6%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. AUS to DEN and DEN to AUS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.