Carrier route record
WNSTL→DTW
Southwest Airlines · St. Louis to Detroit
- Flights
- 611
- Period
- September 2025 to August 2026
- Share of route
- 32%
- Carriers
- 4
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on STL to DTW sits in the middle of the pack with a C+. About seven flights in ten arrive on time by the DOT's definition, 6 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 611 flights, with a median arrival 1 minute late.
The national on-time rate over the same period is 77.3%, so Southwest on STL to DTW runs 6 points behind the country as a whole. Across a thousand flights that is about 58 extra late arrivals.
Key figures
On time
71.5%
Arrivals under 15 minutes late, of 610 completed flights
Avg delay
59 min
Across delayed arrivals only, not all flights
Cancelled
0.16%
National rate is 1.89%
Whole route
81.1%
Every carrier on STL to DTW, 1,899 flights
These figures cover 611 flights between September 2025 and August 2026. Beyond the headline rate, 9.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Southwest against every carrier on STL to DTW
Southwest flew 611 of the 1,899 flights on STL to DTW, about 32% of it. Its 71.5% on time is 10 points worse than the route as a whole, which runs 81.1%. Ranked by on-time rate it is number three of four carriers on the route, where the range runs from Spirit at 100.0% to SkyWest at 71.3%. Two 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 |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Delta Air Lines | 1,104 | 88.2% | 111 min | 1.81% | A |
| Southwest Airlines (this page) | 611 | 71.5% | 59 min | 0.16% | C+ |
| SkyWest Airlinesthin sample | 183 | 71.3% | 110 min | 1.09% | C |
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
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 27 points, against half a point between the best and worst carrier.
- 5am–8am13 flights—
- 8am–11am160 flights86.9%
- 11am–2pm61 flights83.6%
- 2pm–5pm25 flights—
- 5pm–8pm241 flights64.2%
- 8pm–5am111 flights59.5%
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 59.5% on time, against 86.9% 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 5pm–8pm window is the busiest, with 241 flights scheduled in it.
Across the year
Southwest on STL to DTW through the year
June is the worst month at 53.3% on time, 34 points below September, the best at 87.2%. 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. August was the busiest month here, with 62 flights.
Across the week, Friday is the strongest day at 75.5% on time and Thursday the weakest at 61.1%, a spread of 14 points.
Arrival by arrival
How late Southwest on STL to DTW runs when it is late
The 174 late arrivals split 66 under half an hour, 51 between 30 and 60 minutes, and 57 an hour or more.
- 15+ min early50 flights8.2%
- Within 15 min386 flights63.3%
- 15–29 min late66 flights10.8%
- 30–59 min late51 flights8.4%
- 1–2 hours late38 flights6.2%
- 2+ hours late19 flights3.1%
Scale runs 0% to 100%.
Share of 610 completed flights by arrival against schedule.
57 of 224 late departures made up the time and arrived on time, 25% of them. Only 7 left on time and still arrived late.
The worst days
Worst days for Southwest on STL to DTW
The latest arrival of the period was on 6 June 2026, 5 hours 10 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on three of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 6 June 2026 | 5 hours 10 minutes | Late-arriving aircraft |
| 29 July 2026 | 4 hours 16 minutes | Late-arriving aircraft |
| 18 May 2026 | 4 hours 7 minutes | Carrier |
| 16 July 2026 | 3 hours 45 minutes | Late-arriving aircraft |
| 22 August 2026 | 3 hours 44 minutes | National Airspace System |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 65% of the 10,000 delay minutes carriers reported here, and the remaining four split what is left.
- 65%Late-arriving aircraft
- 25%Carrier
- 8%National Airspace System
- 1%Extreme weather
- 0%Security
65% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 10,000 reported delay minutes here, that single category outweighs weather by 53 to one. The split is drawn from 10,247 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 86.9% on time here.
Cancellations are rare at 0.16%, 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 costs
9.3% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection here, and two hours if the onward flight is on a separate ticket.
At 440 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 8am–11am window matters as much as it does.
The return leg runs 74.3% on time across 611 flights, within 3 points 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. 611 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.
What to do with this
Booking Southwest on STL to DTW
Put together: treat all of this as provisional. 611 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 71.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 610 completed flights over 12 months sit behind that.
Related
Where to go next
- STL to DTW, every carrier
- Southwest on DTW to STL, the return leg
- Delta Air Lines on STL to DTW88.2%
- SkyWest Airlines on STL to DTW71.3%
- Southwest Airlines network-wide record
- St. Louis Lambert International (STL) delay statistics
- Detroit Metropolitan Wayne County (DTW) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.