Carrier route record
WNDEN→SDF
Southwest Airlines · Denver to Louisville
- Flights
- 365
- Period
- September 2025 to August 2026
- Share of route
- 33%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on DEN to SDF sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 8 points worse than the national rate of 77.3%. The late ones land roughly 50 minutes behind schedule. That rests on 365 flights, with a median arrival 4 minutes late.
The national on-time rate over the same period is 77.3%, so Southwest on DEN to SDF runs 8 points behind the country as a whole. Across a thousand flights that is about 83 extra late arrivals.
Key figures
On time
69.0%
Arrivals under 15 minutes late, of 361 completed flights
Avg delay
49 min
Across delayed arrivals only, not all flights
Cancelled
1.10%
National rate is 1.89%
Whole route
78.4%
Every carrier on DEN to SDF, 1,095 flights
These figures cover 365 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
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Carrier by carrier
Southwest against every carrier on DEN to SDF
Southwest flew 365 of the 1,095 flights on DEN to SDF, about 33% of it. Its 69.0% on time is 9 points worse than the route as a whole, which runs 78.4%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from United at 83.0% to Southwest at 69.0%.
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 |
|---|---|---|---|---|---|
| United Airlines | 730 | 83.0% | 67 min | 0.68% | B+ |
| Southwest Airlines (this page) | 365 | 69.0% | 49 min | 1.10% | C |
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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 14 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am8 flights—
- 11am–2pm169 flights73.4%
- 2pm–5pm70 flights72.5%
- 5pm–8pm104 flights59.4%
- 8pm–5am14 flights—
Scale runs 50% to 80%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 59.4% on time, against 73.4% for the 11am–2pm 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 11am–2pm window is the busiest, with 169 flights scheduled in it.
Across the year
Southwest on DEN to SDF through the year
May is the best month on the calendar at 87.1% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. March was the busiest month here, with 31 flights.
Across the week, Saturday is the strongest day at 82.0% on time and Monday the weakest at 62.3%, a spread of 20 points.
Arrival by arrival
How late Southwest on DEN to SDF runs when it is late
The 112 late arrivals split 45 under half an hour, 40 between 30 and 60 minutes, and 27 an hour or more.
- 15+ min early23 flights6.4%
- Within 15 min226 flights62.6%
- 15–29 min late45 flights12.5%
- 30–59 min late40 flights11.1%
- 1–2 hours late19 flights5.3%
- 2+ hours late8 flights2.2%
Scale runs 0% to 100%.
Share of 361 completed flights by arrival against schedule.
38 of 138 late departures made up the time and arrived on time, 28% of them. 12 flights left on time and still arrived late.
The worst days
Worst days for Southwest on DEN to SDF
The latest arrival of the period was on 17 February 2026, 4 hours 54 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The five worst days are spread across February, November, August and July, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 17 February 2026 | 4 hours 54 minutes | Late-arriving aircraft |
| 30 November 2025 | 4 hours 36 minutes | Carrier |
| 12 August 2026 | 2 hours 53 minutes | Late-arriving aircraft |
| 8 July 2026 | 2 hours 43 minutes | Carrier |
| 6 August 2026 | 2 hours 23 minutes | National Airspace System |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 58% of the 5,467 delay minutes carriers reported here, and the remaining four split what is left.
- 58%Late-arriving aircraft
- 33%Carrier
- 9%National Airspace System
58% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 5,467 reported delay minutes here, that single category outweighs weather by 58 to one. The split is drawn from 5,467 reported delay minutes.
Cancellations sit at 1.10% against a national 1.89%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here costs
7.5% of arrivals land an hour or more late, close to the national 8.3%, so 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 1,024 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.
The return leg is a different operation and performs like one: it runs 80.6% on time across 366 flights, 12 points above this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 12 points of difference.
One caution: this is a thin sample. 365 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 DEN to SDF
Put together: treat all of this as provisional. 365 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 69.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 361 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to SDF, every carrier
- Southwest on SDF to DEN, the return leg
- United Airlines on DEN to SDF83.0%
- Southwest Airlines network-wide record
- Denver International (DEN) 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.