Carrier route record
WNMKE→DCA
Southwest Airlines · Milwaukee to Washington
- Flights
- 683
- Period
- July 2025 to June 2026
- Share of route
- 51%
- Carriers
- 3
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on MKE to DCA sits in the middle of the pack with a B. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 683 flights, with a median arrival 4 minutes early.
The US average over the same twelve months is 77.6%, so there is little to separate Southwest on MKE to DCA 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 667 completed flights
Avg delay
58 min
Across delayed arrivals only, not all flights
Cancelled
1.90%
National rate is 1.81%
Whole route
75.4%
Every carrier on MKE to DCA, 1,349 flights
These figures cover 683 flights between July 2025 and June 2026. Beyond the headline rate, 8.4% 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 MKE to DCA
Southwest flew 683 of the 1,349 flights on MKE to DCA, most of the route. Its 75.1% on time is about level with the route as a whole at 75.4%. Ranked by on-time rate it is number two of three carriers on the route, where the range runs from PSA at 75.8% to Republic at 57.1%. One 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 |
|---|---|---|---|---|---|
| PSA Airlines | 659 | 75.8% | 134 min | 5.46% | B− |
| Southwest Airlines (this page) | 683 | 75.1% | 58 min | 1.90% | B |
| Republic Airwaysthin sample | 7 | 57.1% | 31 min | 0.00% | D+ |
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 34 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–8am14 flights—
- 8am–11am325 flights90.0%
- 11am–2pm18 flights—
- 2pm–5pm129 flights64.5%
- 5pm–8pm197 flights55.7%
- 8pm–5am—
Scale runs 45% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 55.7% on time, against 90.0% 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 325 flights scheduled in it.
Across the year
Southwest on MKE to DCA through the year
Delays peak in March, when the on-time rate falls to 59.3%. December is the strongest month at 83.3%. Moving a flexible trip across that boundary buys 24 points. July was the busiest month here, with 62 flights.
Across the week, Monday is the strongest day at 81.0% on time and Friday the weakest at 67.7%. 13 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
One category carries most of the weight here. National Airspace System accounts for 46% of the 9,664 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.
- 46%National Airspace System
- 40%Late-arriving aircraft
- 14%Carrier
40% 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 9,664 reported delay minutes here, that single category outweighs weather by 40 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 9,664 reported delay minutes.
46% 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 4,433 minutes out of 9,664, against a national NAS share of 21%.
Cancellations sit at 1.90% against a national 1.81%, which is ordinary. Diversions add another 0.44%.
Connections and stage length
What a delay here costs
8.4% 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 634 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 82.8% on time across 683 flights, 8 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 8 points of difference.
One caution: this is a thin sample. 683 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.
What to do with this
Booking Southwest on MKE to DCA
Put together: treat all of this as provisional. 683 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 75.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 667 completed flights over 12 months sit behind that.
Related
Where to go next
- MKE to DCA, every carrier
- Southwest on DCA to MKE, the return leg
- PSA Airlines on MKE to DCA75.8%
- Southwest Airlines network-wide record
- 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.