Route reliability record
ATL→MKE
Atlanta to Milwaukee
- Flights
- 2,267
- Period
- July 2025 to June 2026
- Distance
- 669 mi
- Carriers
- 2
This route lands a B, 6 points better than the national rate of 77.6%. About one flight in six arrive 15 minutes late or worse, and those flights are late by about 50 minutes on average. That is a workable record, not a spotless one. That rests on 2,267 flights, with a median arrival 6 minutes early.
Set against the rest of the country, this route's record is 6 points better than the US average of 77.6%. That gap is worth roughly 58 fewer late arrivals for every thousand flights.
Key figures
On time
83.4%
Arrivals under 15 minutes late, of 2,219 completed flights
Avg delay
51 min
Across delayed arrivals only, not all flights
Cancelled
1.76%
National rate is 1.81%
Best carrier
Delta
84.2% on time across 2,205 flights
These figures cover 2,267 flights between July 2025 and June 2026. The median arrival is 6 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
Which airline is most reliable on ATL to MKE
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 |
|---|---|---|---|---|---|
| Delta Air Lines | 2,205 | 84.2% | 51 min | 1.81% | B |
| Frontier Airlinesthin sample | 62 | 52.5% | 44 min | 0.00% | F+ |
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 14 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–11am713 flights88.1%
- 11am–2pm294 flights87.6%
- 2pm–5pm518 flights82.7%
- 5pm–8pm294 flights74.0%
- 8pm–5am448 flights80.0%
Scale runs 65% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 88.1% of the time, against 74.0% for the evening window. That is 14 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 713 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 17 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.
December is the weak month at 74.6% on time, against 91.4% in September. 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. May was the busiest month here, with 216 flights.
Across the week, Saturday is the strongest day at 88.1% on time and Monday the weakest at 77.9%. 10 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. Carrier accounts for 50% of the 19,000 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.
- 50%Carrier
- 27%Late-arriving aircraft
- 17%National Airspace System
- 6%Extreme weather
- 0%Security
The largest share of delay minutes, 50%, 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 9,377 of the 19,000 delay minutes reported here. The split is drawn from 18,725 reported delay minutes.
Cancellations sit at 1.76% against a national 1.81%, which is ordinary. Diversions add another 0.35%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 3.9% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.
The 669 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 89.4% on time across 2,267 flights, 6 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 6 points of difference.
The sample behind these figures is 2,267 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. September runs 91.4% on time and December 74.6%, a swing of 17 points. If the dates move at all, move them out of December before you think about anything else. 2,219 completed flights over 12 months sit behind that.
Common questions
ATL to MKE questions
How often is ATL to MKE delayed?
About one flight in six arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 16.6% of the 2,267 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 50 minutes on average.
How reliable is ATL to MKE compared with the rest of the country?
83.4% of flights arrive on time here against a national 77.6%, a difference of 6 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on ATL to MKE?
The 8am–11am departure window is the strongest at 88.1% on time. The 5pm–8pm window is the weakest at 74.0%, 14 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 December delays on ATL to MKE?
December is the weakest month at 74.6% on time, compared with 91.4% in September. Across the year that is 17 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- MKE to ATL — the return legseparate record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Delta Air Lines on-time record84.2%
- Frontier Airlines on-time record52.5%
- The best time of day to fly, according to 7.04 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. ATL to MKE and MKE to ATL 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.