Route reliability record

DEN→MKE

Denver to Milwaukee

Flights: 2,339
Period: July 2025 to June 2026
Distance: 896 mi
Carriers: 4

This route sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 2,339 flights, of which United Airlines flew 741 at 80.5% on time.

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.

On time

75.3%

Arrivals under 15 minutes late, of 2,324 completed flights

Avg delay

66 min

Across delayed arrivals only, not all flights

Cancelled

0.38%

National rate is 1.81%

Best carrier

United

80.5% on time across 741 flights

These figures cover 2,339 flights between July 2025 and June 2026. Beyond the headline rate, 8.7% 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 DEN to MKE

The choice of carrier is not cosmetic here. United Airlines arrives on time 80.5% of the time; Southwest Airlines manages 72.2%. Sample sizes sit next to every figure, because a two-point gap across 1,253 flights means less than a ten-point one.

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	1,253	72.2%	60 min	0.64%	C+

United leads Southwest by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

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 26 points, against 8 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am24 flights—
8am–11am547 flights87.7%
11am–2pm528 flights85.5%
2pm–5pm277 flights71.5%
5pm–8pm709 flights64.0%
8pm–5am254 flights62.2%

Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 62.2% on time, against 87.7% 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 709 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 26 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.

Darker means more delays. Figures are on-time percentages.October best, July worst

July is the worst month at 60.7% on time, 26 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. July was the busiest month here, with 268 flights.

Across the week, Saturday is the strongest day at 80.0% on time and Friday the weakest at 71.4%. 9 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

One category carries most of the weight here. Late-arriving aircraft accounts for 47% of the 38,000 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
47%
Carrier
36%
National Airspace System
14%
Extreme weather
3%

47% 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 38,000 reported delay minutes here, that single category outweighs weather by 18 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 38,003 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 14,000 of the 38,000 delay minutes reported here.

Cancellations are rare at 0.38%, 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 actually costs

8.7% 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 are the about an hour kind, 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 runs 78.1% on time across 2,342 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

The sample behind these figures is 2,339 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 this route

Put together: the calendar is the biggest lever here, not the carrier or the hour. October runs 87.1% on time and July 60.7%, a swing of 26 points. If the dates move at all, move them out of July before you think about anything else. 2,324 completed flights over 12 months sit behind that.

Common questions

DEN to MKE questions

How often is DEN to MKE delayed?

About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 24.7% of the 2,339 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.

Which airline is most reliable on DEN to MKE?

United Airlines leads at 80.5% on time across 741 flights. Southwest Airlines is at the other end on 72.2%, a gap of 8 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 DEN to MKE?

The 8am–11am departure window is the strongest at 87.7% on time. The 8pm–5am window is the weakest at 62.2%, 26 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 July delays on DEN to MKE?

July is the weakest month at 60.7% on time, compared with 87.1% in October. Across the year that is 26 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. DEN to MKE and MKE to DEN are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures