Carrier route record
WNSTL→DCA
Southwest Airlines · St. Louis to Washington
- Flights
- 1,403
- Period
- July 2025 to June 2026
- Share of route
- 58%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on STL to DCA sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 1,403 flights, with a median arrival 2 minutes early.
The national on-time rate over the same period is 77.6%, so Southwest on STL to DCA runs 5 points behind the country as a whole. Across a thousand flights that is about 51 extra late arrivals.
Key figures
On time
72.5%
Arrivals under 15 minutes late, of 1,373 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
1.43%
National rate is 1.81%
Whole route
72.9%
Every carrier on STL to DCA, 2,414 flights
These figures cover 1,403 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% 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
Southwest against every carrier on STL to DCA
Southwest flew 1,403 of the 2,414 flights on STL to DCA, most of the route. Its 72.5% on time is about level with the route as a whole at 72.9%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from Republic at 77.1% to American at 67.5%. Three of those carriers flew fewer than 365 flights here, so treat their positions as rough.
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 |
|---|---|---|---|---|---|
| Republic Airwaysthin sample | 199 | 77.1% | 62 min | 3.52% | B− |
| PSA Airlines | 615 | 74.1% | 128 min | 5.20% | C− |
| Envoy Airthin sample | 22 | 72.7% | 32 min | 0.00% | C+ |
| Southwest Airlines (this page) | 1,403 | 72.5% | 57 min | 1.43% | C |
| American Airlinesthin sample | 175 | 67.5% | 83 min | 2.86% | C |
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 40 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–8am—
- 8am–11am365 flights90.2%
- 11am–2pm353 flights71.0%
- 2pm–5pm346 flights68.6%
- 5pm–8pm253 flights62.5%
- 8pm–5am86 flights50.0%
Scale runs 40% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 50.0% on time, against 90.2% for the 8am–11am slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 8am–11am window is the busiest, with 365 flights scheduled in it.
Across the year
Southwest on STL to DCA through the year
July is the worst month at 53.6% on time, 27 points below April, the best at 80.2%. 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. March was the busiest month here, with 120 flights.
Across the week, Saturday is the strongest day at 83.9% on time and Sunday the weakest at 64.5%. 19 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
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 21,000 reported delay minutes.
- 38%National Airspace System
- 34%Late-arriving aircraft
- 26%Carrier
- 2%Extreme weather
- 0%Security
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 21,000 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 21,266 reported delay minutes.
38% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 7,981 minutes out of 21,000, against a national NAS share of 21%.
Cancellations sit at 1.43% against a national 1.81%, which is ordinary. Diversions add another 0.71%.
Connections and stage length
What a delay here costs
8.2% 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 about an hour, which a normal layover absorbs.
The 719 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg is a different operation and performs like one: it runs 75.7% on time across 1,403 flights, 3 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 3 points of difference.
The sample behind these figures is 1,403 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.
What to do with this
Booking Southwest on STL to DCA
Put together: the calendar is the biggest lever here, not the carrier or the hour. April runs 80.2% on time and July 53.6%, a swing of 27 points. If the dates move at all, move them out of July before you think about anything else. 1,373 completed flights over 12 months sit behind that.
Related
Where to go next
- STL to DCA, every carrier
- Southwest on DCA to STL, the return leg
- Republic Airways on STL to DCA77.1%
- PSA Airlines on STL to DCA74.1%
- American Airlines on STL to DCA67.5%
- Southwest Airlines network-wide record
- St. Louis Lambert International (STL) delay statistics
- Ronald Reagan Washington National (DCA) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.