Route reliability record
SDF→ATL
Louisville to Atlanta
- Flights
- 2,707
- Period
- July 2025 to June 2026
- Distance
- 321 mi
- Carriers
- 2
This route earns a A. Close to nine flights in ten arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 12 points better than the national rate of 77.6%. When something does go wrong the average delay runs an hour and a half. That rests on 2,707 flights, with a median arrival 18 minutes early.
Set against the rest of the country, this route's record is 12 points better than the US average of 77.6%. That gap is worth roughly 124 fewer late arrivals for every thousand flights.
Key figures
On time
90.0%
Arrivals under 15 minutes late, of 2,661 completed flights
Avg delay
88 min
Across delayed arrivals only, not all flights
Cancelled
1.59%
National rate is 1.81%
Best carrier
Delta
90.0% on time across 2,705 flights
These figures cover 2,707 flights between July 2025 and June 2026. The median arrival is 18 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 SDF to ATL
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 | 90.0% | 89 min | 1.59% | A |
| Spirit Airlinesthin sample | 2 | 50.0% | 21 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–8am710 flights92.3%
- 8am–11am676 flights91.4%
- 11am–2pm435 flights90.8%
- 2pm–5pm376 flights87.6%
- 5pm–8pm402 flights86.1%
- 8pm–5am108 flights85.7%
Scale runs 75% to 100%. Rows with fewer than 30 flights show a dash.
The early departures do better, though not dramatically: 92.3% on time for the 5am–8am window against 85.7% for 8pm–5am. Worth taking if the schedule allows, not worth an extra connection. The 5am–8am window is the busiest, with 710 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 14 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.
December is the weak month at 84.6% on time, against 98.6% in September. 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 263 flights.
Across the week, Wednesday is the strongest day at 93.7% on time and Sunday the weakest at 86.0%. 8 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 23,000 reported delay minutes.
- 36%Late-arriving aircraft
- 35%Carrier
- 22%National Airspace System
- 7%Extreme weather
36% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 23,000 reported delay minutes here, that single category outweighs weather by 5 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 23,487 reported delay minutes.
The largest share of delay minutes, 35%, 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 8,122 of the 23,000 delay minutes reported here.
Cancellations sit at 1.59% against a national 1.81%, which is ordinary. Diversions add another 0.11%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.5% 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 84.9% on time across 2,707 flights, 5 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 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 98.6% on time and December 84.6%, a swing of 14 points. If the dates move at all, move them out of December before you think about anything else. 2,661 completed flights over 12 months sit behind that.
Common questions
SDF to ATL questions
How often is SDF to ATL delayed?
About one flight in ten arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 10.0% of the 2,707 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
How reliable is SDF to ATL compared with the rest of the country?
90.0% of flights arrive on time here against a national 77.6%, a difference of 12 points in its favour. That is worth a A on this site's grading scale.
What time of day has the fewest delays on SDF to ATL?
The 5am–8am departure window is the strongest at 92.3% on time. The 8pm–5am window is the weakest at 85.7%, 7 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 December delays on SDF to ATL?
December is the weakest month at 84.6% on time, compared with 98.6% in September. Across the year that is 14 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
- ATL to SDF — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Delta Air Lines on-time record90.0%
- Spirit Airlines on-time record50.0%
- Why the first flight of the morning is statistically safest
- Worst months to fly in the US, ranked by the data
Direction matters. SDF to ATL and ATL to SDF 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.