Route reliability record
DTW→SDF
Detroit to Louisville
- Flights
- 1,190
- Period
- July 2025 to June 2026
- Distance
- 306 mi
- Carriers
- 4
This route lands a B, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That is a workable record, not a spotless one. That rests on 1,190 DTW to SDF flights, of which Republic Airways flew 408 at 80.0% on time.
Best time to fly DTW to SDF: a 8am–11am departure, ideally on a Saturday. Flights in that window arrived on time 81.2% of the time and Saturday flights 84.9%, against 77.2% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
77.2%
Arrivals under 15 minutes late, of 1,175 completed flights
Avg delay
83 min
Across delayed arrivals only, not all flights
Cancelled
1.18%
National rate is 1.81%
Best carrier
Republic
80.0% on time across 408 flights
These figures cover 1,190 flights between July 2025 and June 2026. Beyond the headline rate, 9.3% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.
Carrier by carrier
Which airline is most reliable on DTW to SDF
The two carriers here are closely matched: 4 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 18 | 83.3% | 39 min | 0.00% | B+ |
| Republic Airways | 408 | 80.0% | 94 min | 0.74% | B+ |
| SkyWest Airlines | 753 | 76.0% | 79 min | 1.46% | B |
| Delta Air Linesthin sample | 11 | 45.5% | 88 min | 0.00% | F+ |
No carrier stands out. Republic tops the table at 80.0%, 4 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
Flights on DTW to SDF
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
Best ways to make this trip
The most reliable ways to fly Detroit to Louisville
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. DTW → SDFDetroit to Louisville | Republic Airways | 79.4% | 80.0% | 0.74% | 2pm–5pm, Fri | YX 5832 19:45 |
| 2. DTW → SDFDetroit to Louisville | SkyWest Airlines | 74.9% | 76.0% | 1.46% | 8am–11am, Sat | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 12 points, against 4 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am351 flights81.2%
- 11am–2pm226 flights79.5%
- 2pm–5pm186 flights68.9%
- 5pm–8pm187 flights71.7%
- 8pm–5am240 flights79.8%
Scale runs 60% to 85%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 81.2% of the time, against 68.9% for the afternoon window. That is 12 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 351 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 34 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 61.6% on time, against 95.9% 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. July was the busiest month here, with 124 flights.
Across the week, Saturday is the strongest day at 84.9% on time and Friday the weakest at 73.1%. 12 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 56% of the 22,000 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.
- 56%Carrier
- 18%Extreme weather
- 16%Late-arriving aircraft
- 10%National Airspace System
Extreme weather accounts for 18% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.9 times the usual weather exposure. The split is drawn from 22,208 reported delay minutes.
The largest share of delay minutes, 56%, 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 12,000 of the 22,000 delay minutes reported here.
Cancellations sit at 1.18% against a national 1.81%, which is ordinary. Diversions add another 0.08%.
Connections and stage length
What a delay here actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.3% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
At 306 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 8am–11am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 81.9% on time across 1,190 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 1,190 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.
Work out the risk of missing a connection in SDF after this flight
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 95.9% on time and December 61.6%, a swing of 34 points. If the dates move at all, move them out of December before you think about anything else. 1,175 completed flights over 12 months sit behind that.
Common questions
DTW to SDF questions
How often is DTW to SDF delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.8% of the 1,190 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.
Which airline is most reliable on DTW to SDF?
Republic Airways leads at 80.0% on time across 408 flights. SkyWest Airlines is at the other end on 76.0%, a gap of 4 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on DTW to SDF?
The 8am–11am departure window is the strongest at 81.2% on time. The 2pm–5pm window is the weakest at 68.9%, 12 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 DTW to SDF?
December is the weakest month at 61.6% on time, compared with 95.9% in September. Across the year that is 34 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 DTW — the return legseparate record
- Detroit Metropolitan Wayne County (DTW) delay statistics
- Republic Airways on DTW to SDF80.0%
- SkyWest Airlines on DTW to SDF76.0%
- DTW to ORD, a related route72.0%
- ORD to SDF, a related route75.3%
- DTW to ATL, a related route79.0%
- Spirit Airlines on-time record83.3%
- Republic Airways on-time record80.0%
- SkyWest Airlines on-time record76.0%
- How often a connection fails at the major US hubs
- The best time of day to fly, according to 7.04 million flight records
Direction matters. DTW to SDF and SDF to DTW are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.