Route reliability record
SDF→DCA
Louisville to Washington
- Flights
- 1,029
- Period
- July 2025 to June 2026
- Distance
- 474 mi
- Carriers
- 4
This route carries a cancellation problem, not just a delay problem: 4.7% of scheduled flights never operate, against 1.8% nationally. Of the ones that do fly, about four flights in five 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 1,029 SDF to DCA flights, of which Republic Airways flew 439 at 86.3% on time.
Best time to fly SDF to DCA: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 91.8% of the time and Saturday flights 86.3%, against 78.9% 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
78.9%
Arrivals under 15 minutes late, of 978 completed flights
Avg delay
96 min
Across delayed arrivals only, not all flights
Cancelled
4.66%
National rate is 1.81%
Best carrier
Republic
86.3% on time across 439 flights
These figures cover 1,029 flights between July 2025 and June 2026. Beyond the headline rate, 8.1% 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 SDF to DCA
The choice of carrier is not cosmetic here. Republic Airways arrives on time 86.3% of the time; PSA Airlines manages 72.8%. Sample sizes sit next to every figure, because a two-point gap across 572 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Envoy Airthin sample | 13 | 91.7% | 38 min | 7.69% | A− |
| Republic Airways | 439 | 86.3% | 56 min | 1.59% | A |
| PSA Airlines | 572 | 72.8% | 113 min | 6.99% | C− |
| American Airlinesthin sample | 5 | 60.0% | 69 min | 0.00% | D+ |
PSA Airlines cancels 7.0% 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 SDF to DCA
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 Louisville to Washington
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. 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 32 points, against 14 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am357 flights91.8%
- 8am–11am141 flights85.6%
- 11am–2pm203 flights76.3%
- 2pm–5pm160 flights59.5%
- 5pm–8pm165 flights67.1%
- 8pm–5am3 flights—
Scale runs 50% 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 59.5% for the afternoon window. That is 32 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 357 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.
June is the worst month at 69.1% on time, 18 points below October, the best at 87.1%. 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 93 flights.
Across the week, Saturday is the strongest day at 86.3% on time and Wednesday the weakest at 76.0%. 10 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 20,000 reported delay minutes.
- 38%Late-arriving aircraft
- 37%Carrier
- 24%National Airspace System
- 1%Extreme weather
- 0%Security
38% 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 20,000 reported delay minutes here, that single category outweighs weather by 31 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 19,674 reported delay minutes.
The largest share of delay minutes, 37%, 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 7,260 of the 20,000 delay minutes reported here.
Cancellations run at 4.66%, against 1.81% nationally. That is about one flight in twenty 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
8.1% 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 an hour and a half, 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 75.1% on time across 1,031 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. 1,029 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 DCA after this flight
What to do with this
Booking this route
Put together: the delay figures matter less here than the 4.66% cancellation rate. A late arrival costs you an hour and a half; 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. 978 completed flights over 12 months sit behind that.
Common questions
SDF to DCA questions
How often is SDF to DCA delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.1% of the 1,029 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 SDF to DCA?
Republic Airways leads at 86.3% on time across 439 flights. PSA Airlines is at the other end on 72.8%, a gap of 14 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 SDF to DCA?
The 5am–8am departure window is the strongest at 91.8% on time. The 2pm–5pm window is the weakest at 59.5%, 32 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 June delays on SDF to DCA?
June is the weakest month at 69.1% on time, compared with 87.1% in October. 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
- DCA to SDF — the return legseparate record
- Ronald Reagan Washington National (DCA) delay statistics
- Republic Airways on SDF to DCA86.3%
- PSA Airlines on SDF to DCA72.8%
- SDF to ORD, a related route79.0%
- BOS to DCA, a related route74.0%
- SDF to ATL, a related route90.0%
- Envoy Air on-time record91.7%
- Republic Airways on-time record86.3%
- PSA Airlines on-time record72.8%
- The US routes with the most cancellations
- Why the first flight of the morning is statistically safest
Direction matters. SDF to DCA and DCA 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.