Carrier route record
UADEN→SDF
United Airlines · Denver to Louisville
- Flights
- 730
- Period
- September 2025 to August 2026
- Share of route
- 67%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with United Airlines.
United on DEN to SDF lands a B+, 6 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about an hour on average. That rests on 730 flights, with a median arrival 6 minutes early.
Set against the rest of the country, United's DEN to SDF record is 6 points better than the US average of 77.3%. That gap is worth roughly 57 fewer late arrivals for every thousand flights.
Key figures
On time
83.0%
Arrivals under 15 minutes late, of 725 completed flights
Avg delay
67 min
Across delayed arrivals only, not all flights
Cancelled
0.68%
National rate is 1.89%
Whole route
78.4%
Every carrier on DEN to SDF, 1,095 flights
These figures cover 730 flights between September 2025 and August 2026. The median arrival is 6 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
United against every carrier on DEN to SDF
United flew 730 of the 1,095 flights on DEN to SDF, most of the route. Its 83.0% on time is 5 points better than the route as a whole, which runs 78.4%. Ranked by on-time rate it is first 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 (this page) | 730 | 83.0% | 67 min | 0.68% | B+ |
| Southwest Airlines | 365 | 69.0% | 49 min | 1.10% | C |
Flight by flight
United flight numbers on DEN to SDF
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Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 15 points, against half a point between the best and worst carrier.
- 5am–8am1 flights—
- 8am–11am365 flights90.4%
- 11am–2pm1 flights—
- 2pm–5pm—
- 5pm–8pm363 flights75.8%
- 8pm–5am—
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 90.4% of the time, against 75.8% for the evening window. That is 15 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 365 flights scheduled in it.
Across the year
United on DEN to SDF through the year
April is the best month on the calendar at 93.4% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. May was the busiest month here, with 63 flights.
Across the week, Tuesday is the strongest day at 88.3% on time and Thursday the weakest at 74.0%, a spread of 14 points.
Arrival by arrival
How late United on DEN to SDF runs when it is late
United on DEN to SDF often beats the schedule: 190 of 725 completed flights, 26%, arrived 15 minutes or more early. The 123 late arrivals split 39 under half an hour, 42 between 30 and 60 minutes, and 42 an hour or more.
- 15+ min early190 flights26.2%
- Within 15 min412 flights56.8%
- 15–29 min late39 flights5.4%
- 30–59 min late42 flights5.8%
- 1–2 hours late24 flights3.3%
- 2+ hours late18 flights2.5%
Scale runs 0% to 100%.
Share of 725 completed flights by arrival against schedule.
22 of 115 late departures made up the time and arrived on time, 19% of them. 30 flights left on time and still arrived late.
The worst days
Worst days for United on DEN to SDF
The latest arrival of the period was on 22 August 2026, 10 hours 4 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). Three of the five worst days fell in August 2026.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 22 August 2026 | 10 hours 4 minutes | Carrier |
| 28 July 2026 | 5 hours 21 minutes | Late-arriving aircraft |
| 6 March 2026 | 4 hours 4 minutes | Late-arriving aircraft |
| 14 August 2026 | 3 hours 24 minutes | Late-arriving aircraft |
| 13 August 2026 | 3 hours 21 minutes | Late-arriving aircraft |
Delay causes
Why United runs late on this route
Late-arriving aircraft accounts for 49% of the 8,257 delay minutes carriers reported here, and the remaining four split what is left.
- 49%Late-arriving aircraft
- 30%Carrier
- 20%National Airspace System
- 1%Extreme weather
49% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 8,257 reported delay minutes here, that single category outweighs weather by 44 to one. The split is drawn from 8,257 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 90.4% on time here.
Cancellations are rare at 0.68%, 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
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 runs 85.8% on time across 730 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. 730 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 United on DEN to SDF
Put together: treat all of this as provisional. 730 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 83.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 725 completed flights over 12 months sit behind that.
Related
Where to go next
- DEN to SDF, every carrier
- United on SDF to DEN, the return leg
- Southwest Airlines on DEN to SDF69.0%
- United 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.