Route reliability record
SDF→MDW
Louisville to Chicago
- Flights
- 989
- Period
- July 2025 to June 2026
- Distance
- 271 mi
- Carriers
- 1
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 989 SDF to MDW flights, with a median arrival 9 minutes early.
Best time to fly SDF to MDW: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 91.8% of the time and Saturday flights 87.4%, against 84.4% for the route overall.
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 68 fewer late arrivals for every thousand flights.
Key figures
On time
84.4%
Arrivals under 15 minutes late, of 964 completed flights
Avg delay
63 min
Across delayed arrivals only, not all flights
Cancelled
2.12%
National rate is 1.81%
Best carrier
Southwest
84.4% on time across 989 flights
These figures cover 989 flights between July 2025 and June 2026. The median arrival is 9 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 MDW
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 |
|---|---|---|---|---|---|
| Southwest Airlines | 989 | 84.4% | 63 min | 2.12% | B |
Best ways to make this trip
The most reliable ways to fly Louisville to Chicago
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SDF → MDWLouisville to Chicago | Southwest Airlines | 82.6% | 84.4% | 2.12% | 5am–8am, Sat | — |
| 2. SDF → ORDLouisville to Chicago | Republic Airways | 80.3% | 82.5% | 2.71% | 5am–8am, Thu | YX 3422 07:00 |
| 3. SDF → ORDLouisville to Chicago | Envoy Air | 76.4% | 77.5% | 1.44% | 8am–11am, Thu | — |
| 4. SDF → ORDLouisville to Chicago | SkyWest Airlines | 68.1% | 70.9% | 3.88% | 5am–8am, Thu | — |
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 17 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am247 flights91.8%
- 8am–11am127 flights87.2%
- 11am–2pm95 flights89.1%
- 2pm–5pm192 flights83.1%
- 5pm–8pm176 flights79.4%
- 8pm–5am152 flights74.5%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 91.8% of the time, against 74.5% for the overnight window. That is 17 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 247 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 18 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.
Delays peak in March, when the on-time rate falls to 77.1%. February is the strongest month at 94.6%. Moving a flexible trip across that boundary buys 18 points. July was the busiest month here, with 104 flights.
Across the week, Saturday is the strongest day at 87.4% on time and Thursday the weakest at 79.1%. 8 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. Late-arriving aircraft accounts for 54% of the 9,429 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.
- 54%Late-arriving aircraft
- 24%National Airspace System
- 20%Carrier
- 1%Extreme weather
54% 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 9,429 reported delay minutes here, that single category outweighs weather by 54 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 9,429 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 91.8% on time here.
Cancellations sit at 2.12% against a national 1.81%, which is ordinary. Diversions add another 0.40%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.8% 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 271 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 80.6% on time across 990 flights, 4 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 4 points of difference.
One caution: this is a thin sample. 989 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
Work out the risk of missing a connection in MDW after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 989 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 84.4% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 964 completed flights over 12 months sit behind that.
Common questions
SDF to MDW questions
How often is SDF to MDW delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 15.6% of the 989 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is SDF to MDW compared with the rest of the country?
84.4% 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 SDF to MDW?
The 5am–8am departure window is the strongest at 91.8% on time. The 8pm–5am window is the weakest at 74.5%, 17 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 SDF to MDW?
March is the weakest month at 77.1% on time, compared with 94.6% in February. Across the year that is 18 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
- MDW to SDF — the return legseparate record
- Chicago Midway International (MDW) delay statistics
- SDF to ORD, a related route79.0%
- ATL to MDW, a related route76.3%
- SDF to ATL, a related route90.0%
- Southwest Airlines on-time record84.4%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. SDF to MDW and MDW to SDF 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.