Carrier route record
UASDF→DEN
United Airlines · Louisville to Denver
- Flights
- 731
- Period
- July 2025 to June 2026
- Share of route
- 66%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on SDF to DEN earns a B+. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 7 points better than the national rate of 77.6%. When something does go wrong the average delay runs about an hour. That rests on 731 flights, with a median arrival 10 minutes early.
Set against the rest of the country, United's SDF to DEN record is 7 points better than the US average of 77.6%. That gap is worth roughly 70 fewer late arrivals for every thousand flights.
Key figures
On time
84.6%
Arrivals under 15 minutes late, of 723 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
0.96%
National rate is 1.81%
Whole route
83.0%
Every carrier on SDF to DEN, 1,103 flights
These figures cover 731 flights between July 2025 and June 2026. The median arrival is 10 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.
Carrier by carrier
United against every carrier on SDF to DEN
United flew 731 of the 1,103 flights on SDF to DEN, most of the route. Its 84.6% on time is 2 points better than the route as a whole, which runs 83.0%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from United at 84.6% to Southwest at 79.8%.
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) | 731 | 84.6% | 66 min | 0.96% | B+ |
| Southwest Airlines | 372 | 79.8% | 55 min | 1.08% | B |
Flight by flight
United flight numbers on SDF to DEN
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 13 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am365 flights91.2%
- 11am–2pm1 flights—
- 2pm–5pm364 flights78.5%
- 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 78.5% for the afternoon window. That is 13 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, Tuesday is the strongest day at 89.6% on time and Sunday the weakest at 78.4%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Carrier accounts for 55% of the 7,280 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 55%Carrier
- 31%National Airspace System
- 11%Late-arriving aircraft
- 4%Extreme weather
The largest share of delay minutes, 55%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 3,974 of the 7,280 delay minutes reported here. The split is drawn from 7,280 reported delay minutes.
Cancellations sit at 0.96% against a national 1.81%, which is ordinary. Diversions add another 0.14%.
Connections and stage length
What a delay here costs
5.0% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says 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. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg is a different operation and performs like one: it runs 80.9% on time across 731 flights, 4 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 4 points of difference.
One caution: this is a thin sample. 731 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. 731 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 84.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 723 completed flights over 12 months sit behind that.
Related
Where to go next
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.