Route reliability record
AUS→STL
Austin to St. Louis
- Flights
- 977
- Period
- July 2025 to June 2026
- Distance
- 721 mi
- Carriers
- 1
This route lands a B+, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 977 AUS to STL flights, with a median arrival 3 minutes early.
Best time to fly AUS to STL: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 95.6% of the time and Tuesday flights 84.4%, against 77.3% 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
77.3%
Arrivals under 15 minutes late, of 974 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
0.10%
National rate is 1.81%
Best carrier
Southwest
77.3% on time across 977 flights
These figures cover 977 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 AUS to STL
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 | 977 | 77.3% | 52 min | 0.10% | 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 52 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–8am343 flights95.6%
- 8am–11am17 flights—
- 11am–2pm241 flights77.5%
- 2pm–5pm263 flights68.1%
- 5pm–8pm112 flights43.8%
- 8pm–5am1 flights—
Scale runs 35% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 43.8% on time, against 95.6% 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. The 5am–8am window is the busiest, with 343 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 29 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 60.0% on time, 29 points below January, the best at 88.7%. 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. May was the busiest month here, with 93 flights.
Across the week, Tuesday is the strongest day at 84.4% on time and Sunday the weakest at 70.2%. 14 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 60% of the 11,000 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.
- 60%Late-arriving aircraft
- 30%Carrier
- 9%National Airspace System
- 1%Extreme weather
- 0%Security
60% 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 11,000 reported delay minutes here, that single category outweighs weather by 55 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 11,432 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 95.6% on time here.
Cancellations are rare at 0.10%, 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
5.9% 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 roughly 50 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 76.8% on time across 976 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. 977 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 STL after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 977 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 77.3% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 974 completed flights over 12 months sit behind that.
Common questions
AUS to STL questions
How often is AUS to STL delayed?
Roughly 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 22.7% of the 977 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 50 minutes on average.
How reliable is AUS to STL compared with the rest of the country?
77.3% of flights arrive on time here against a national 77.6%, a difference of half a point against it. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on AUS to STL?
The 5am–8am departure window is the strongest at 95.6% on time. The 5pm–8pm window is the weakest at 43.8%, 52 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 AUS to STL?
June is the weakest month at 60.0% on time, compared with 88.7% in January. Across the year that is 29 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
- STL to AUS — the return legseparate record
- Austin-Bergstrom International (AUS) delay statistics
- St. Louis Lambert International (STL) delay statistics
- AUS to DEN, a related route78.4%
- ATL to STL, a related route82.4%
- AUS to DFW, a related route73.8%
- Southwest Airlines on-time record77.3%
- 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. AUS to STL and STL to AUS 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.