Carrier route record
UASDF→DEN
United Airlines · Louisville to Denver
- 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 SDF to DEN earns an A+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.3%. When something does go wrong the average delay runs a little over an hour. That rests on 730 flights, with a median arrival 11 minutes early.
Set against the rest of the country, United's SDF to DEN record is 9 points better than the US average of 77.3%. That gap is worth roughly 85 fewer late arrivals for every thousand flights.
Key figures
On time
85.8%
Arrivals under 15 minutes late, of 718 completed flights
Avg delay
72 min
Across delayed arrivals only, not all flights
Cancelled
0.96%
National rate is 1.89%
Whole route
84.1%
Every carrier on SDF to DEN, 1,096 flights
These figures cover 730 flights between September 2025 and August 2026. The median arrival is 11 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 SDF to DEN
United flew 730 of the 1,096 flights on SDF to DEN, most of the route. Its 85.8% on time is 2 points better than the route as a whole, which runs 84.1%. Ranked by on-time rate it is first 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 (this page) | 730 | 85.8% | 72 min | 0.96% | A+ |
| Southwest Airlines | 366 | 80.6% | 55 min | 1.09% | B |
Flight by flight
United flight numbers on SDF to DEN
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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 11 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am365 flights91.2%
- 11am–2pm1 flights—
- 2pm–5pm363 flights80.7%
- 5pm–8pm1 flights—
- 8pm–5am—
Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 91.2% of the time, against 80.7% for the afternoon window. That is 11 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 SDF to DEN through the year
December is the weak month at 72.1% on time, against 95.2% in October. 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 63 flights.
Across the week, Saturday is the strongest day at 89.1% on time and Sunday the weakest at 81.4%, a spread of 8 points.
Arrival by arrival
How late United on SDF to DEN runs when it is late
United on SDF to DEN often beats the schedule: 273 of 718 completed flights, 38%, arrived 15 minutes or more early. The 102 late arrivals split 38 under half an hour, 25 between 30 and 60 minutes, and 39 an hour or more.
- 15+ min early273 flights38.0%
- Within 15 min343 flights47.8%
- 15–29 min late38 flights5.3%
- 30–59 min late25 flights3.5%
- 1–2 hours late21 flights2.9%
- 2+ hours late18 flights2.5%
Scale runs 0% to 100%.
Share of 718 completed flights by arrival against schedule.
27 of 99 late departures made up the time and arrived on time, 27% of them. 30 flights left on time and still arrived late.
The worst days
Worst days for United on SDF to DEN
The latest arrival of the period was on 4 January 2026, 7 hours 37 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The same cause led on four of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 4 January 2026 | 7 hours 37 minutes | Carrier |
| 3 November 2025 | 6 hours 25 minutes | Carrier |
| 19 February 2026 | 5 hours 16 minutes | Carrier |
| 19 August 2026 | 4 hours 20 minutes | Carrier |
| 17 February 2026 | 4 hours 9 minutes | National Airspace System |
Delay causes
Why United runs late on this route
Carrier accounts for 54% of the 7,379 delay minutes carriers reported here, and the remaining four split what is left.
- 54%Carrier
- 27%National Airspace System
- 14%Late-arriving aircraft
- 5%Extreme weather
The largest share of delay minutes, 54%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,971 of the 7,379 delay minutes reported here. The split is drawn from 7,379 reported delay minutes.
Cancellations sit at 0.96% against a national 1.89%, which is ordinary. Diversions add another 0.68%.
Connections and stage length
What a delay here costs
5.4% 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 a little over 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 83.0% 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 SDF to DEN
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 85.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 718 completed flights over 12 months sit behind that.
Related
Where to go next
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.