Carrier route record
WNATL→STL
Southwest Airlines · Atlanta to St. Louis
- Flights
- 1,130
- Period
- July 2025 to June 2026
- Share of route
- 30%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on ATL to STL 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 about an hour on average. That is a workable record, not a spotless one. That rests on 1,130 flights, with a median arrival 7 minutes early.
The US average over the same twelve months is 77.6%, so there is little to separate Southwest on ATL to STL from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
79.9%
Arrivals under 15 minutes late, of 1,124 completed flights
Avg delay
56 min
Across delayed arrivals only, not all flights
Cancelled
0.53%
National rate is 1.81%
Whole route
82.4%
Every carrier on ATL to STL, 3,706 flights
These figures cover 1,130 flights between July 2025 and June 2026. The median arrival is 7 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
Southwest against every carrier on ATL to STL
Southwest flew 1,130 of the 3,706 flights on ATL to STL, about 30% of it. Its 79.9% on time is 3 points worse than the route as a whole, which runs 82.4%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from Delta at 84.7% to Frontier at 69.7%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
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 |
|---|---|---|---|---|---|
| Delta Air Lines | 2,371 | 84.7% | 55 min | 1.98% | B |
| Southwest Airlines (this page) | 1,130 | 79.9% | 56 min | 0.53% | B+ |
| Frontier Airlinesthin sample | 205 | 69.7% | 57 min | 1.95% | C |
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 38 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–8am134 flights93.3%
- 8am–11am237 flights93.2%
- 11am–2pm202 flights86.6%
- 2pm–5pm192 flights73.3%
- 5pm–8pm191 flights75.9%
- 8pm–5am174 flights55.5%
Scale runs 45% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 55.5% on time, against 93.3% 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 8am–11am window is the busiest, with 237 flights scheduled in it.
Across the year
Southwest on ATL to STL through the year
June is the worst month at 67.4% on time, 21 points below January, the best at 88.8%. 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 114 flights.
Across the week, Wednesday is the strongest day at 91.0% on time and Sunday the weakest at 68.7%. 22 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 61% of the 13,000 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.
- 61%Late-arriving aircraft
- 30%Carrier
- 5%National Airspace System
- 3%Extreme weather
- 1%Security
61% 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 13,000 reported delay minutes here, that single category outweighs weather by 20 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 12,678 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 93.3% on time here.
Cancellations are rare at 0.53%, 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
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 about an hour, which a normal layover absorbs.
At 484 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg runs 80.7% on time across 1,130 flights, within about a point 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 1,130 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 Southwest on ATL to STL
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 88.8% on time and June 67.4%, a swing of 21 points. If the dates move at all, move them out of June before you think about anything else. 1,124 completed flights over 12 months sit behind that.
Related
Where to go next
- ATL to STL, every carrier
- Southwest on STL to ATL, the return leg
- Delta Air Lines on ATL to STL84.7%
- Frontier Airlines on ATL to STL69.7%
- Southwest Airlines network-wide record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- St. Louis Lambert International (STL) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.