Best time to fly out of Louisville (SDF)

The early-flight folk wisdom holds up at Louisville Muhammad Ali: departures in the Before 6am band left on time 92.8% of the time, against 66.1% in the 8–10pm band. These are historical odds, not forecasts. The records say what happened on this schedule over three years; they know nothing about tomorrow’s thunderstorm.

Data through June 2026 · Bureau of Transportation Statistics

On-time rate by hour and day

On this page, “on time” means a departure that pushed back less than 15 minutes behind its scheduled time — the Bureau of Transportation Statistics definition, and the one airlines are held to.

Share of departures that left on time, by hour band and day of week.
Departure time MonTueWedThuFriSatSun
Before 6am 94 92 91 94 94 92 94
6–8am 91 92 93 92 90 90 90
8–10am 89 92 93 92 89 90 88
10am–12pm 86 86 88 86 83 83 83
12–2pm 82 87 87 84 82 82 81
2–4pm 80 84 85 77 77 80 75
4–6pm 77 80 78 73 73 75 71
6–8pm 74 75 75 68 73 71 68
8–10pm 66 76 72 66 67 71 59
10pm–12am – – – – – – –
fewer left on time more left on time

The steadiest stretch at SDF was Before 6am — 92.8% of departures left on time across 2,128 flights. The weakest was 8–10pm at 66.1%. 6–8am departures from SDF left on time 91.1% of the time across 17,252 flights; 6–8pm departures, 71.9% across 6,938. That is a gap of 19.2 points, and it is the whole case for the early flight.

The year at SDF

July was the hard month at SDF: 76.8% of departures left on time, across 6,518 flights. October was the easy one at 87.5%. Each month pools three years of that month, so a single bad week does not decide it.

Share of departures that left on time, by calendar month. Best month in green, worst in amber. The hairline sits at the overall rate, 83.1%.
Departure on-time share at SDF by calendar month
Month Share departures that left on time Flights
January 82.5% 5,034
February 85.9% 4,852
March 82.4% 5,939
April 84.2% 6,132
May 79.7% 6,724
June 78.6% 6,282
July 76.8% 6,518
August 84.4% 6,141
September 86.8% 5,993
October 87.5% 6,412
November 86.9% 5,520
December 83% 5,363

Airlines at SDF

Every airline with at least 100 departures from SDF, busiest first. These are that airline’s departures from this airport only — its record across the country sits on its own page.

Airline Left on time Typical delay Cancelled Departures
Republic Airways 89% 69 min 1.8% 17,713
Southwest Airlines 82.1% 57 min 1.1% 15,440
American Airlines 78.8% 118 min 2.1% 7,790
Delta Air Lines 88.5% 84 min 1.2% 7,570
SkyWest Airlines 81.9% 99 min 1.6% 5,869
PSA Airlines 76.9% 114 min 3.3% 5,148
Envoy Air 81% 67 min 1.5% 3,752
United Airlines 83.5% 81 min 0.9% 2,584
Spirit Airlines 71.4% 72 min 1.9% 2,458
Allegiant Air 72.2% 98 min 1.2% 2,159
Endeavor Air 85.3% 80 min 1.2% 427

Spirit Airlines (through May 2026) and Endeavor Air (through December 2024) stopped filing before June 2026. Their rows cover a shorter run of months than the rest of the table, so their figures are not set against the others anywhere on this page.

What delays out of SDF were put down to

Airlines file a reason with every arrival running 15 minutes late or more. Across 12,434 flights that departed SDF and ran 15 minutes late or more, the delay minutes break down with 37% put down to airline operations and 35.4% to late-arriving aircraft.

Late-arriving aircraft 35.4% Airline operations 37% Air traffic & airport volume 22.1% Severe weather 5.3% Security 0.2%
  • Late-arriving aircraft 35.4%
  • Airline operations 37%
  • Air traffic & airport volume 22.1%
  • Severe weather 5.3%
  • Security 0.2%

Late-arriving aircraft is the knock-on category: the plane came in late, so it went out late again. It is why a 7am problem in Newark is still a problem in Denver at dinnertime, and why it is usually the biggest slice on the bar.

If you are connecting through SDF

Of 70,908 scheduled arrivals into SDF, 77.4% reached the gate less than 15 minutes behind schedule. Of the 14,742 arrivals that ran late, 53.7% were no more than 45 minutes behind — which is the difference between a tight connection and a new boarding pass.

Work out a specific layover — pick the airport and the minutes you have, and the tool reads the same arrival records back as a share.

Busiest routes out of SDF

Ranked by flights, with the share that arrived on time at the far end. Where a route carries enough flights for a page of its own the chip goes there; otherwise it goes to the destination airport.

SDF in one number

Louisville Muhammad Ali (SDF)

Rank 60 of 363 US airports by departures. Steadiest stretch of the day: Before 6am. Hardest month: July.

July 2023–June 2026 · 69,748 departures flown

83.1% of departures left on time

Questions about SDF

What is the best time of day to fly out of Louisville Muhammad Ali?
Before 6am. Departures in that band left on time 92.8% of the time across 2,128 flights, July 2023 through June 2026 — the best of the ten bands in the day. The 8–10pm band was the weakest at 66.1%.
Is the early flight out of SDF really more reliable?
6–8am departures from SDF left on time 91.1% of the time across 17,252 flights; 6–8pm departures, 71.9% across 6,938. That is a gap of 19.2 points, and it is the whole case for the early flight.
What is the worst month to fly out of SDF?
July: 76.8% of the departures that flew left on time, with 6,518 scheduled. October was the other end of the year at 87.5%. Each figure pools three years of that calendar month.
Which airline is most on time at SDF?
Republic Airways — 89% of its 17,713 departures from SDF left on time. Allegiant Air sat at the other end at 72.2% over 2,159 flights. Only airlines with at least 100 departures here are ranked. Airlines that stopped filing before June 2026 are left out of the ranking — their figures cover a shorter run of months than the rest of the table.
How often are flights cancelled at SDF?
1.6% of scheduled departures were cancelled over July 2023 through June 2026. Cancellations are counted against everything scheduled, not against everything that flew — a rate that looks small still adds up to real people in a rebooking line.