Carrier route record

WNDEN→MKE

Southwest Airlines · Denver to Milwaukee

Flights: 1,253
Period: July 2025 to June 2026
Share of route: 54%
Carriers: 4

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on DEN to MKE 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 1,253 flights, with a median arrival right on schedule.

The national on-time rate over the same period is 77.6%, so Southwest on DEN to MKE runs 5 points behind the country as a whole. Across a thousand flights that is about 54 extra late arrivals.

On time

72.2%

Arrivals under 15 minutes late, of 1,243 completed flights

Avg delay

60 min

Across delayed arrivals only, not all flights

Cancelled

0.64%

National rate is 1.81%

Whole route

75.3%

Every carrier on DEN to MKE, 2,339 flights

These figures cover 1,253 flights between July 2025 and June 2026. Beyond the headline rate, 9.9% 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

Southwest against every carrier on DEN to MKE

Southwest flew 1,253 of the 2,339 flights on DEN to MKE, most of the route. Its 72.2% on time is 3 points worse than the route as a whole, which runs 75.3%. Ranked by on-time rate it is last of four carriers on the route, where the range runs from Frontier at 86.7% to Southwest at 72.2%. Two 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.

On-time performance by carrier on DEN to MKE
Airline	Flights	On time	Avg delay	Cancelled	Grade
Frontier Airlinesthin sample	60	86.7%	92 min	0.00%	A+
United Airlines	741	80.5%	71 min	0.00%	B+
SkyWest Airlinesthin sample	285	73.0%	82 min	0.35%	C+
Southwest Airlines (this page)	1,253	72.2%	60 min	0.64%	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 32 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–8am24 flights—
8am–11am312 flights88.1%
11am–2pm230 flights83.3%
2pm–5pm223 flights68.2%
5pm–8pm345 flights56.4%
8pm–5am119 flights59.3%

Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 56.4% on time, against 88.1% 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 5pm–8pm window is the busiest, with 345 flights scheduled in it.

Across the year

Southwest on DEN to MKE through the year

Darker means more delays. Figures are on-time percentages.January best, August worst

August is the worst month at 60.4% on time, 25 points below January, the best at 84.9%. 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. July was the busiest month here, with 141 flights.

Across the week, Tuesday is the strongest day at 77.2% on time and Friday the weakest at 66.1%. 11 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. Late-arriving aircraft accounts for 54% of the 21,000 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.

Late-arriving aircraft
54%
Carrier
36%
National Airspace System
9%
Extreme weather
2%

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 21,000 reported delay minutes here, that single category outweighs weather by 33 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 20,800 reported delay minutes.

The largest share of delay minutes, 36%, 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 7,463 of the 21,000 delay minutes reported here.

Cancellations are rare at 0.64%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 9.9% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

The 896 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 79.5% on time across 1,255 flights, 7 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 7 points of difference.

The sample behind these figures is 1,253 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 DEN to MKE

Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 84.9% on time and August 60.4%, a swing of 25 points. If the dates move at all, move them out of August before you think about anything else. 1,243 completed flights over 12 months sit behind that.

Where to go next

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.

Key figures