Route reliability record
STL→AUS
St. Louis to Austin
- Flights
- 976
- Period
- July 2025 to June 2026
- Distance
- 721 mi
- Carriers
- 1
This route lands a B+, about a point worse than the national rate of 77.6%. About one flight in four arrives 15 minutes late or worse, and those flights are late by about 55 minutes on average. That is a workable record, not a spotless one. That rests on 976 STL to AUS flights, with a median arrival 3 minutes early.
Best time to fly STL to AUS: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 87.6% of the time and Wednesday flights 83.9%, against 76.8% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.8%
Arrivals under 15 minutes late, of 970 completed flights
Avg delay
54 min
Across delayed arrivals only, not all flights
Cancelled
0.41%
National rate is 1.81%
Best carrier
Southwest
76.8% on time across 976 flights
These figures cover 976 flights between July 2025 and June 2026. The median arrival is 3 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
Which airline is most reliable on STL to AUS
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 976 | 76.8% | 54 min | 0.41% | B+ |
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 34 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am17 flights—
- 8am–11am340 flights87.6%
- 11am–2pm27 flights—
- 2pm–5pm262 flights71.4%
- 5pm–8pm42 flights53.7%
- 8pm–5am288 flights71.6%
Scale runs 45% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 53.7% on time, against 87.6% 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 8am–11am window is the busiest, with 340 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 27 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 62.8% on time, 27 points below January, the best at 90.2%. 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. July was the busiest month here, with 93 flights.
Across the week, Wednesday is the strongest day at 83.9% on time and Sunday the weakest at 69.2%. 15 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 62% of the 12,000 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.
- 62%Late-arriving aircraft
- 22%Carrier
- 14%National Airspace System
- 2%Extreme weather
- 0%Security
62% 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 12,000 reported delay minutes here, that single category outweighs weather by 37 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 12,202 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 87.6% on time here.
Cancellations are rare at 0.41%, 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 actually costs
6.1% 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 55 minutes, which a normal layover absorbs.
The 721 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 77.3% on time across 977 flights, within half a point 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. 976 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.
Work out the risk of missing a connection in AUS after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 976 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 76.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 970 completed flights over 12 months sit behind that.
Common questions
STL to AUS questions
How often is STL to AUS 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 976 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 55 minutes on average.
How reliable is STL to AUS compared with the rest of the country?
76.8% of flights arrive on time here against a national 77.6%, a difference of about a point against it. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on STL to AUS?
The 8am–11am departure window is the strongest at 87.6% on time. The 5pm–8pm window is the weakest at 53.7%, 34 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 STL to AUS?
June is the weakest month at 62.8% on time, compared with 90.2% in January. Across the year that is 27 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
- AUS to STL — the return legseparate record
- St. Louis Lambert International (STL) delay statistics
- Austin-Bergstrom International (AUS) delay statistics
- STL to ATL, a related route85.3%
- DEN to AUS, a related route76.1%
- STL to DEN, a related route74.9%
- Southwest Airlines on-time record76.8%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. STL to AUS and AUS to STL 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.