Route reliability record
ATL→SDF
Atlanta to Louisville
- Flights
- 2,707
- Period
- July 2025 to June 2026
- Distance
- 321 mi
- Carriers
- 2
This route 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 2,707 flights, with a median arrival 8 minutes early.
Set against the rest of the country, this route's record is 7 points better than the US average of 77.6%. That gap is worth roughly 73 fewer late arrivals for every thousand flights.
Key figures
On time
84.9%
Arrivals under 15 minutes late, of 2,660 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
1.51%
National rate is 1.81%
Best carrier
Delta
84.9% on time across 2,705 flights
These figures cover 2,707 flights between July 2025 and June 2026. The median arrival is 8 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
Which airline is most reliable on ATL to SDF
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 |
|---|---|---|---|---|---|
| Delta Air Lines | 2,705 | 84.9% | 64 min | 1.52% | B |
| Spirit Airlinesthin sample | 2 | 50.0% | 42 min | 0.00% | F+ |
Departure window
The best time of day to leave
Departure time is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 2,707 flights.
- 5am–8am74 flights91.3%
- 8am–11am682 flights89.6%
- 11am–2pm365 flights85.9%
- 2pm–5pm401 flights82.6%
- 5pm–8pm448 flights81.5%
- 8pm–5am737 flights82.7%
Scale runs 75% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.3% of the time, against 81.5% for the evening window. That is 10 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 737 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 15 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
September is the best month on the calendar at 93.7% 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 263 flights.
Across the week, Wednesday is the strongest day at 89.3% on time and Sunday the weakest at 78.5%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Carrier accounts for 49% of the 26,000 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.
- 49%Carrier
- 24%Late-arriving aircraft
- 19%National Airspace System
- 9%Extreme weather
- 0%Security
The largest share of delay minutes, 49%, 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 13,000 of the 26,000 delay minutes reported here. The split is drawn from 25,845 reported delay minutes.
Cancellations sit at 1.51% against a national 1.81%, which is ordinary. Diversions add another 0.22%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.7% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
At 321 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 90.0% on time across 2,707 flights, 5 points above 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 5 points of difference.
The sample behind these figures is 2,707 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 93.7% on time and March 78.6%, a swing of 15 points. If the dates move at all, move them out of March before you think about anything else. 2,660 completed flights over 12 months sit behind that.
Common questions
ATL to SDF questions
How often is ATL to SDF delayed?
About one flight in seven arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 15.1% of the 2,707 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is ATL to SDF compared with the rest of the country?
84.9% of flights arrive on time here against a national 77.6%, a difference of 7 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on ATL to SDF?
The 5am–8am departure window is the strongest at 91.3% on time. The 5pm–8pm window is the weakest at 81.5%, 10 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are March delays on ATL to SDF?
March is the weakest month at 78.6% on time, compared with 93.7% in September. Across the year that is 15 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- SDF to ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Delta Air Lines on-time record84.9%
- Spirit Airlines on-time record50.0%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. ATL to SDF and SDF to ATL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.