Carrier route record

WNMKE→DEN

Southwest Airlines · Milwaukee to Denver

Flights: 1,255
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 MKE to DEN lands a B+, 2 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 1,255 flights, with a median arrival 5 minutes early.

The US average over the same twelve months is 77.6%, so there is little to separate Southwest on MKE to DEN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.

On time

79.5%

Arrivals under 15 minutes late, of 1,245 completed flights

Avg delay

59 min

Across delayed arrivals only, not all flights

Cancelled

0.64%

National rate is 1.81%

Whole route

78.1%

Every carrier on MKE to DEN, 2,342 flights

These figures cover 1,255 flights between July 2025 and June 2026. The median arrival is 5 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Southwest against every carrier on MKE to DEN

Southwest flew 1,255 of the 2,342 flights on MKE to DEN, most of the route. Its 79.5% on time is about level with the route as a whole at 78.1%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from Southwest at 79.5% to Frontier at 71.7%. 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 MKE to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
Southwest Airlines (this page)	1,255	79.5%	59 min	0.64%	B+
SkyWest Airlinesthin sample	285	77.5%	65 min	0.35%	B+
United Airlines	742	76.6%	63 min	0.13%	B+
Frontier Airlinesthin sample	60	71.7%	91 min	0.00%	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 42 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–8am397 flights95.9%
8am–11am175 flights86.2%
11am–2pm179 flights78.2%
2pm–5pm128 flights72.2%
5pm–8pm297 flights64.2%
8pm–5am79 flights53.8%

Scale runs 45% to 100%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 53.8% on time, against 95.9% for the 5am–8am 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 5am–8am window is the busiest, with 397 flights scheduled in it.

Across the year

Southwest on MKE to DEN through the year

Darker means more delays. Figures are on-time percentages.February best, December worst

December is the weak month at 68.9% on time, against 87.5% in February. 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. July was the busiest month here, with 141 flights.

Across the week, Friday is the strongest day at 82.6% on time and Monday the weakest at 77.2%. 5 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 15,000 reported delay minutes.

Late-arriving aircraft
41%
National Airspace System
32%
Carrier
26%
Extreme weather
1%

41% 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 15,000 reported delay minutes here, that single category outweighs weather by 41 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 15,049 reported delay minutes.

32% 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 4,834 minutes out of 15,000, against a national NAS share of 21%.

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

6.3% 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 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 72.2% on time across 1,253 flights, 7 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 7 points of difference.

The sample behind these figures is 1,255 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 MKE to DEN

Put together: the calendar is the biggest lever here, not the carrier or the hour. February runs 87.5% on time and December 68.9%, a swing of 19 points. If the dates move at all, move them out of December before you think about anything else. 1,245 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