79% of flights leaving Louisville (SDF) arrived on time over the past 12 months, 4 points better than the national average of 76%. That ranks 21 of 76 large U.S. airports. About 73 flights leave SDF on a typical day; 2.2% were cancelled. 80% pushed back from the gate on time, so most of the lateness is already there when the flight leaves the gate.
At a glance
- Best hour to fly: 5 a.m. (92% on time). Worst: 6 p.m. (66%).
- Best month: October (86%). Worst: July (74%).
- Most reliable airline here: Delta Air Lines (82%), vs American Airlines at 77%.
- Biggest delay cause: late-arriving aircraft (39% of delay minutes).
- Year on year: about the same (80% → 79%).
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for flights leaving SDF: when a flight was late, it was under 45 minutes late 49% of the time. About 1 in 14 flights landed an hour or more late, and 1 in 59 three hours or more; 2.2% were cancelled outright.
- On time or early79%
- 15–30 min late5.9%
- 30–60 min late5.2%
- 1–2 hours late4.0%
- 2–3 hours late1.4%
- 3+ hours late1.7%
- Diverted0.3%
- Cancelled2.2%
Share of all 26,698 scheduled flights, past 12 months, by arrival time against schedule.
Best time of day to fly out of SDF
Time of day matters more at SDF than almost anything else you control. Flights scheduled to leave at 5 a.m. arrived on time 92% of the time; at 6 p.m. it was 66%, a 26-point gap. Taken together, early departures (5–9 a.m.) ran 88% on time against 67% for the evening bank (5–10 p.m.). Early planes usually start the day at the airport, so they haven't had a chance to pick up delays elsewhere. By evening a late inbound aircraft, a crew running out of duty hours or an afternoon thunderstorm can push one late flight into the next. Cancellations cluster too: 8 p.m. departures were cancelled 3.5% of the time, against 2.2% overall.
Hour × month
Combine the two and the spread is wider still. The most reliable combination at SDF was a 5 a.m. departure in May (96% on time); the least, 8 p.m. in July (52%). If you can only move one thing, move the hour. Departure hour usually shifts the odds more than the month does.
Each cell: on-time rate for that departure hour in that calendar month, 2023–2026. Find your travel month, then look along the row for the greenest hour.
Best and worst months
July is the hardest month at SDF, with 74% of flights on time across 2023–2026; October is the best at 86%. Summer (June–August) runs 8 points worse than autumn: heavy schedules, peak loads and afternoon thunderstorms. Winter costs 6 points against autumn. Cancellations peak in January (5.1% of flights).
Airlines at SDF
American Airlines runs 30% of departures from SDF. Among airlines with at least 1,000 departures here, Delta Air Lines was the most reliable (82% on time) and American Airlines the least (77%), a 5-point difference. On a route where both fly, that difference is worth more than a small fare gap.
| Airline | Departures | On time | Left on time | Cancelled | Typical arrival |
|---|---|---|---|---|---|
| American Airlines | 7,881 | 77% | 78% | 2.9% | −11 min |
| Delta Air Lines | 6,716 | 82% | 82% | 2.0% | −13 min |
| United Airlines | 5,722 | 80% | 83% | 2.3% | −10 min |
| Southwest Airlines | 5,313 | 81% | 79% | 1.4% | −7 min |
| Allegiant Air | 774 | 62% | 64% | 0.9% | 0 min |
| Spirit Airlines | 292 | 74% | 70% | 6.5% | −10 min |
Why flights are late at SDF
Airlines report a cause for every flight that arrives 15 or more minutes late. At SDF, 39% of delay minutes came from late-arriving aircraft: the plane showed up late from its previous flight, so the delay started somewhere else. Next is the airlines themselves at 33%. That's why the first flight of the morning is the safest bet: it has no earlier flight to inherit a delay from. Of the 597 cancellations, 58% were blamed on weather.
The average taxi from gate to takeoff is 16 minutes, about typical for a large U.S. airport.
Month by month
Over the latest 12 months 79% of SDF departures were on time, against 80% in the 12 months before: essentially unchanged. The best recent month was September 2025 (87%); the worst, December 2025 (73%).
Worst cancellation days
The worst single day in the past year was Sunday, Jan 25, 2026, when 86% of 64 scheduled departures were cancelled. Days like that are usually a major storm, a system outage or a holiday peak hitting bad weather. No average predicts them, so on a stormy forecast, check your airline's travel waivers.
| Date | Departures | Cancelled | On time |
|---|---|---|---|
| Jan 25, 2026 | 64 | 86% | 3% |
| Jan 26, 2026 | 66 | 39% | 35% |
| Jan 24, 2026 | 52 | 29% | 40% |
| Nov 5, 2025 | 66 | 24% | 45% |
| Mar 16, 2026 | 74 | 19% | 24% |
| Feb 23, 2026 | 69 | 19% | 64% |
| Feb 22, 2026 | 70 | 16% | 51% |
| Mar 15, 2026 | 79 | 15% | 66% |
| Jul 28, 2026 | 74 | 15% | 70% |
| Mar 7, 2026 | 65 | 14% | 60% |
Last flights of the day
The last flight of the day is a different bet. Across routes from SDF, each airline's final departure was cancelled 3.1% of the time, against 2.1% for its earlier flights (1.5× as often). Late in the day crews run short on duty hours, aircraft arrive late from elsewhere, and with no later flight to fold passengers into, cancelling is easier for the airline. 2.2% of last flights landed 3+ hours late. The riskiest last flight out was American Airlines to Dallas (5.2% cancelled).
| Last flight to | Airline | Leaves | Cancelled | 3h+ late | On time |
|---|---|---|---|---|---|
| DFW Dallas | American Airlines | 7:48 p.m. | 5.2% | 5.0% | 58% |
| ORD Chicago | United Airlines | 7:55 p.m. | 4.9% | 4.9% | 57% |
| DCA Washington | American Airlines | 2:27 p.m. | 6.1% | 2.3% | 60% |
| ORD Chicago | American Airlines | 7:10 p.m. | 6.9% | 1.4% | 65% |
| LGA New York | Delta Air Lines | 5:57 p.m. | 5.5% | 1.7% | 70% |
| DTW Detroit | Delta Air Lines | 5:26 p.m. | 1.4% | 5.5% | 70% |
| EWR Newark | United Airlines | 1:07 p.m. | 5.0% | 1.1% | 75% |
| PHL Philadelphia | American Airlines | 6:25 p.m. | 3.9% | 1.7% | 72% |
| CLT Charlotte | American Airlines | 8:08 p.m. | 3.0% | 1.9% | 75% |
| MSP Minneapolis | Delta Air Lines | 7:51 p.m. | 2.3% | 2.3% | 71% |
| BWI Baltimore | Southwest Airlines | 5:00 p.m. | 2.5% | 1.4% | 74% |
| MCO Orlando | Southwest Airlines | 5:30 p.m. | 2.5% | 1.2% | 63% |
Each airline's last scheduled departure of the day on a route, on days it flies the route at least twice; past 12 months. Riskiest first.
Tips for flying out of SDF
- Book the earliest departure you can live with. At SDF the 5 a.m. flights do best.
- Traveling in July? Leave extra slack for anything that can't move: cruises, weddings, the last connection of the day.
- Choosing between airlines? Delta Air Lines has the better record here.
- Need to arrive tonight? Don't book the last flight out of SDF; the one before it leaves you a backup.
- Delayed already? Most delays at SDF come from late-arriving aircraft. If your inbound plane is late, your flight will be too, whatever the board says.
Routes from SDF
Where you're going matters too. From SDF, the most reliable busy route was to Atlanta (ATL, 88% on time) and the least reliable to Dallas (DFW, 73%). Flights into congested airports inherit their delays: an air traffic program at the destination holds planes on the ground here.
Least reliable first. Routes with at least 365 flights a year.
| To | Flights | On time | Cancelled | Typical arrival |
|---|---|---|---|---|
| BOS Boston | 709 | 69% | 2.1% | −6 min |
| DFW Dallas | 1,994 | 73% | 3.1% | −10 min |
| DCA Washington | 1,025 | 74% | 4.6% | −8 min |
| ORD Chicago | 3,315 | 74% | 3.1% | −6 min |
| MSP Minneapolis | 1,084 | 76% | 1.5% | −7 min |
| LGA New York | 1,202 | 77% | 4.7% | −12 min |
| BNA Nashville | 544 | 78% | 0.9% | −2 min |
| MCO Orlando | 865 | 79% | 1.8% | −6 min |
| DTW Detroit | 1,306 | 80% | 0.9% | −10 min |
| CLT Charlotte | 1,776 | 80% | 2.4% | −12 min |
| TPA Tampa | 405 | 80% | 2.0% | −5 min |
| PHL Philadelphia | 986 | 81% | 2.4% | −14 min |
| MDW Chicago | 976 | 82% | 1.6% | −8 min |
| PHX Phoenix | 369 | 82% | 1.1% | −8 min |
| EWR Newark | 1,034 | 83% | 4.6% | −13 min |
| LAS Las Vegas | 399 | 83% | 0.8% | −7 min |
| DEN Denver | 1,096 | 83% | 1.0% | −8 min |
| IAH Houston | 1,076 | 83% | 1.0% | −15 min |
| MIA Miami | 407 | 84% | 1.7% | −11 min |
| BWI Baltimore | 880 | 85% | 1.8% | −10 min |
| IAD Washington | 866 | 88% | 0.8% | −10 min |
| ATL Atlanta | 2,754 | 88% | 1.5% | −18 min |
Flights into SDF
Arriving rather than leaving? These are the routes into Louisville Muhammad Ali, least reliable first. The weakest is from Miami (63% on time).
| From | Flights | On time | Cancelled |
|---|---|---|---|
| MIA Miami | 408 | 63% | 1.5% |
| PHX Phoenix | 369 | 69% | 0.5% |
| LAS Las Vegas | 399 | 69% | 1.0% |
| DFW Dallas | 1,992 | 70% | 2.9% |
| BNA Nashville | 545 | 71% | 0.4% |
| DCA Washington | 1,027 | 71% | 5.4% |
| ORD Chicago | 3,312 | 72% | 3.6% |
| MCO Orlando | 865 | 73% | 2.2% |
| CLT Charlotte | 1,776 | 74% | 2.4% |
| MSP Minneapolis | 1,083 | 75% | 1.6% |
| DTW Detroit | 1,306 | 76% | 1.3% |
| LGA New York | 1,201 | 76% | 4.1% |
| EWR Newark | 1,035 | 76% | 5.7% |
| DEN Denver | 1,095 | 78% | 0.8% |
| BWI Baltimore | 891 | 78% | 2.5% |
| PHL Philadelphia | 987 | 79% | 2.7% |
| IAD Washington | 867 | 82% | 1.0% |
| MDW Chicago | 966 | 82% | 1.7% |
| ATL Atlanta | 2,754 | 83% | 1.5% |
| BOS Boston | 709 | 83% | 1.7% |
| IAH Houston | 1,075 | 84% | 1.0% |
| TPA Tampa | 404 | 85% | 0.5% |
Questions about SDF delays
What is the best time to fly out of SDF?
Flights scheduled at 5 a.m.: over the past year 92% of SDF departures at that hour arrived on time, against 66% at 6 p.m., the worst hour.
What month has the most flight delays at SDF?
July (74% on time). October is the best month (86%).
Which airline is most on time at SDF?
Delta Air Lines: 82% of its SDF departures arrived on time over the past year. American Airlines had the weakest record at 77%.
Why are flights delayed at SDF?
The biggest cause was late-arriving aircraft (39% of delay minutes): the plane showed up late from its previous flight, so the delay started somewhere else. Then the airlines themselves (33%).
How often are flights cancelled at SDF?
2.2% of scheduled departures over the past 12 months, peaking in January at 5.1%.
Hours are scheduled local departure times. "On time" means arriving less than 15 minutes late at the destination; cancelled and diverted flights count as not on time. Method.