Route reliability record
DCA→SDF
Washington to Louisville
- Flights
- 1,031
- Period
- July 2025 to June 2026
- Distance
- 474 mi
- Carriers
- 4
This route carries a cancellation problem, not just a delay problem: 6.5% of scheduled flights never operate, against 1.8% nationally. Of the ones that do fly, close to three flights in four arrive on time, worth a B− overall. The punctuality figure counts only flights that actually departed, so it flatters an operation that cancels this often. That rests on 1,031 DCA to SDF flights, of which Republic Airways flew 441 at 75.4% on time.
Best time to fly DCA to SDF: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 92.3% of the time and Saturday flights 83.9%, against 75.1% 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
75.1%
Arrivals under 15 minutes late, of 963 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
6.50%
National rate is 1.81%
Best carrier
Republic
75.4% on time across 441 flights
These figures cover 1,031 flights between July 2025 and June 2026. Beyond the headline rate, 8.9% 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 DCA to SDF
The two carriers here are closely matched: about a point 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 |
|---|---|---|---|---|---|
| Envoy Airthin sample | 13 | 83.3% | 42 min | 7.69% | B− |
| American Airlinesthin sample | 5 | 80.0% | 66 min | 0.00% | B+ |
| Republic Airways | 441 | 75.4% | 79 min | 6.80% | B− |
| PSA Airlines | 572 | 74.6% | 61 min | 6.29% | C− |
Republic Airways cancels 6.8% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Flight by flight
Flights on DCA 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 Washington to Louisville
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. 1 of the top 3 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. BWI → SDFBaltimore to Louisville | Southwest Airlines | 76.9% | 78.9% | 2.48% | 11am–2pm, Wed | — |
| 2. DCA → SDFWashington to Louisville | Republic Airways | 70.3% | 75.4% | 6.80% | 8am–11am, Sat | YX 4672 19:59 |
| 3. DCA → SDFWashington to Louisville | PSA Airlines | 69.9% | 74.6% | 6.29% | 5am–8am, 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 24 points, against about a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am82 flights92.3%
- 8am–11am257 flights80.8%
- 11am–2pm39 flights81.6%
- 2pm–5pm212 flights68.4%
- 5pm–8pm289 flights69.4%
- 8pm–5am152 flights74.3%
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 92.3% of the time, against 68.4% for the afternoon window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 289 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 32 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 55.2% on time, against 87.1% in October. 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. October was the busiest month here, with 93 flights.
Across the week, Saturday is the strongest day at 83.9% on time and Wednesday the weakest at 65.7%. 18 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 16,000 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.
- 54%Late-arriving aircraft
- 25%Carrier
- 13%National Airspace System
- 8%Extreme weather
- 0%Security
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 16,000 reported delay minutes here, that single category outweighs weather by 7 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 16,340 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 92.3% on time here.
Cancellations run at 6.50%, against 1.81% nationally. That is about one flight in fifteen cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and stage length
What a delay here actually costs
8.9% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.
At 474 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 1,029 flights, 4 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 4 points of difference.
One caution: this is a thin sample. 1,031 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 SDF after this flight
What to do with this
Booking this route
Put together: the delay figures matter less here than the 6.50% cancellation rate. A late arrival costs you a little over an hour; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 963 completed flights over 12 months sit behind that.
Common questions
DCA to SDF questions
How often is DCA to SDF delayed?
About 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 24.9% of the 1,031 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on DCA to SDF?
Republic Airways leads at 75.4% on time across 441 flights. PSA Airlines is at the other end on 74.6%, a gap of about a point. 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 DCA to SDF?
The 5am–8am departure window is the strongest at 92.3% on time. The 2pm–5pm window is the weakest at 68.4%, 24 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 DCA to SDF?
December is the weakest month at 55.2% on time, compared with 87.1% in October. Across the year that is 32 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 DCA — the return legseparate record
- Ronald Reagan Washington National (DCA) delay statistics
- Republic Airways on DCA to SDF75.4%
- PSA Airlines on DCA to SDF74.6%
- DCA to BOS, a related route71.4%
- ORD to SDF, a related route75.3%
- DCA to ORD, a related route74.3%
- Envoy Air on-time record83.3%
- American Airlines on-time record80.0%
- Republic Airways on-time record75.4%
- The US routes with the most cancellations
- Why the first flight of the morning is statistically safest
Direction matters. DCA to SDF and SDF to DCA 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.