Route reliability record
SDF→BWI
Louisville to Baltimore
- Flights
- 889
- Period
- July 2025 to June 2026
- Distance
- 495 mi
- Carriers
- 1
This route earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 8 points better than the national rate of 77.6%. When something does go wrong the average delay runs a little over an hour. That rests on 889 SDF to BWI flights, with a median arrival 10 minutes early.
Best time to fly SDF to BWI: a 5am–8am departure, ideally on a Monday. Flights in that window arrived on time 94.8% of the time and Monday flights 91.7%, against 85.7% for the route overall.
Set against the rest of the country, this route's record is 8 points better than the US average of 77.6%. That gap is worth roughly 81 fewer late arrivals for every thousand flights.
Key figures
On time
85.7%
Arrivals under 15 minutes late, of 868 completed flights
Avg delay
72 min
Across delayed arrivals only, not all flights
Cancelled
2.25%
National rate is 1.81%
Best carrier
Southwest
85.7% on time across 889 flights
These figures cover 889 flights between July 2025 and June 2026. The median arrival is 10 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 BWI
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 | 889 | 85.7% | 72 min | 2.25% | A |
Best ways to make this trip
The most reliable ways to fly Louisville to Baltimore
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. 2 of the top 3 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SDF → DCALouisville to Washington | Republic Airways | 84.9% | 86.3% | 1.59% | 5am–8am, Wed | YX 4549 06:00 |
| 2. SDF → BWILouisville to Baltimore | Southwest Airlines | 83.8% | 85.7% | 2.25% | 5am–8am, Mon | — |
| 3. SDF → DCALouisville to Washington | PSA Airlines | 67.7% | 72.8% | 6.99% | 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 27 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–8am351 flights94.8%
- 8am–11am64 flights82.8%
- 11am–2pm110 flights91.7%
- 2pm–5pm231 flights80.5%
- 5pm–8pm128 flights67.5%
- 8pm–5am5 flights—
Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 94.8% of the time, against 67.5% for the evening window. That is 27 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 351 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 23 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.
July is the worst month at 72.4% on time, 23 points below January, the best at 94.9%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. October was the busiest month here, with 95 flights.
Across the week, Monday is the strongest day at 91.7% on time and Sunday the weakest at 77.4%. 14 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 8,962 reported delay minutes.
- 40%Carrier
- 34%Late-arriving aircraft
- 24%National Airspace System
- 2%Extreme weather
34% 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 8,962 reported delay minutes here, that single category outweighs weather by 17 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 8,962 reported delay minutes.
The largest share of delay minutes, 40%, 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 3,585 of the 8,962 delay minutes reported here.
Cancellations sit at 2.25% 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 4.3% 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 495 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 78.9% on time across 888 flights, 7 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 7 points of difference.
One caution: this is a thin sample. 889 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 BWI after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 889 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 85.7% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 868 completed flights over 12 months sit behind that.
Common questions
SDF to BWI questions
How often is SDF to BWI delayed?
About one flight in seven arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 14.3% of the 889 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
How reliable is SDF to BWI compared with the rest of the country?
85.7% of flights arrive on time here against a national 77.6%, a difference of 8 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 BWI?
The 5am–8am departure window is the strongest at 94.8% on time. The 5pm–8pm window is the weakest at 67.5%, 27 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 July delays on SDF to BWI?
July is the weakest month at 72.4% on time, compared with 94.9% in January. Across the year that is 23 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
- BWI to SDF — the return legseparate record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- SDF to ORD, a related route79.0%
- ATL to BWI, a related route75.6%
- SDF to ATL, a related route90.0%
- Southwest Airlines on-time record85.7%
- 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 BWI and BWI 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.