Carrier route record
WNSDF→DEN
Southwest Airlines · Louisville to Denver
- Flights
- 366
- 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 SDF to DEN lands a B, 3 points better than the national rate of 77.3%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 366 flights, with a median arrival 3 minutes early.
The US average over the same twelve months is 77.3%, so there is little to separate Southwest on SDF to DEN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
80.6%
Arrivals under 15 minutes late, of 361 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
1.09%
National rate is 1.89%
Whole route
84.1%
Every carrier on SDF to DEN, 1,096 flights
These figures cover 366 flights between September 2025 and August 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.
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Carrier by carrier
Southwest against every carrier on SDF to DEN
Southwest flew 366 of the 1,096 flights on SDF to DEN, about 33% of it. Its 80.6% on time is 4 points worse than the route as a whole, which runs 84.1%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from United at 85.8% to Southwest at 80.6%.
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 | 85.8% | 72 min | 0.96% | A+ |
| Southwest Airlines (this page) | 366 | 80.6% | 55 min | 1.09% | B |
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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 30 points, against half a point between the best and worst carrier.
- 5am–8am90 flights95.5%
- 8am–11am12 flights—
- 11am–2pm158 flights79.5%
- 2pm–5pm56 flights65.5%
- 5pm–8pm50 flights72.0%
- 8pm–5am—
Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 95.5% of the time, against 65.5% for the afternoon window. That is 30 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 158 flights scheduled in it.
Across the year
Southwest on SDF to DEN through the year
December is the weak month at 64.5% on time, against 96.7% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. May was the busiest month here, with 32 flights.
Across the week, Wednesday is the strongest day at 86.3% on time and Monday the weakest at 74.5%, a spread of 12 points.
Arrival by arrival
How late Southwest on SDF to DEN runs when it is late
The 70 late arrivals split 32 under half an hour, 17 between 30 and 60 minutes, and 21 an hour or more.
- 15+ min early66 flights18.3%
- Within 15 min225 flights62.3%
- 15–29 min late32 flights8.9%
- 30–59 min late17 flights4.7%
- 1–2 hours late13 flights3.6%
- 2+ hours late8 flights2.2%
Scale runs 0% to 100%.
Share of 361 completed flights by arrival against schedule.
21 of 79 late departures made up the time and arrived on time, 27% of them. 12 flights left on time and still arrived late.
The worst days
Worst days for Southwest on SDF to DEN
The latest arrival of the period was on 28 October 2025, 5 hours 18 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across October, August, December and March, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 28 October 2025 | 5 hours 18 minutes | Carrier |
| 22 August 2026 | 3 hours 20 minutes | Carrier |
| 19 December 2025 | 3 hours 13 minutes | National Airspace System |
| 24 October 2025 | 2 hours 56 minutes | Late-arriving aircraft |
| 6 March 2026 | 2 hours 42 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 47% of the 3,866 delay minutes carriers reported here, and the remaining four split what is left.
- 47%Late-arriving aircraft
- 31%Carrier
- 22%National Airspace System
- 0%Extreme weather
47% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 3,866 reported delay minutes here, that single category outweighs weather by 47 to one. The split is drawn from 3,866 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 95.5% on time here.
Cancellations sit at 1.09% against a national 1.89%, which is ordinary. Diversions add another 0.27%.
Connections and stage length
What a delay here costs
5.8% 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 about an hour, 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 69.0% on time across 365 flights, 12 points below 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. 366 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 SDF to DEN
Put together: treat all of this as provisional. 366 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 80.6% 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
- SDF to DEN, every carrier
- Southwest on DEN to SDF, the return leg
- United Airlines on SDF to DEN85.8%
- 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.