Carrier route record

DLMDW→ATL

Delta Air Lines · Chicago to Atlanta

Flights: 1,383
Period: July 2025 to June 2026
Share of route: 39%
Carriers: 3

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

Delta on MDW to ATL earns an A. More than four flights in five arrive inside the 15-minute window the DOT uses to define an on-time arrival, which puts it 9 points better than the national rate of 77.6%. When something does go wrong the average delay runs an hour and a half. That rests on 1,383 flights. The strongest carrier on the route with a full sample, Southwest Airlines, flew 1,546 at 76.7% on time.

Set against the rest of the country, Delta's MDW to ATL record is 9 points better than the US average of 77.6%. That gap is worth roughly 93 fewer late arrivals for every thousand flights.

On time

86.9%

Arrivals under 15 minutes late, of 1,343 completed flights

Avg delay

93 min

Across delayed arrivals only, not all flights

Cancelled

2.53%

National rate is 1.81%

Whole route

79.8%

Every carrier on MDW to ATL, 3,528 flights

These figures cover 1,383 flights between July 2025 and June 2026. The median arrival is 17 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

Delta against every carrier on MDW to ATL

Delta flew 1,383 of the 3,528 flights on MDW to ATL, about 39% of it. Its 86.9% on time is 7 points better than the route as a whole, which runs 79.8%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from Delta at 86.9% to Frontier at 71.8%.

The two carriers here are closely matched: 5 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.

On-time performance by carrier on MDW to ATL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)	1,383	86.9%	93 min	2.53%	A
Southwest Airlines	1,546	76.7%	57 min	1.29%	B
Frontier Airlines	599	71.8%	52 min	1.67%	C

No carrier stands out. Southwest tops the table at 76.7%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.

Flight by flight

Delta flight numbers on MDW to ATL

Departure window

When Delta runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 13 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am365 flights91.5%
8am–11am289 flights88.7%
11am–2pm343 flights86.7%
2pm–5pm92 flights78.4%
5pm–8pm294 flights82.4%
8pm–5am—

Scale runs 70% to 95%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 91.5% of the time, against 78.4% for the afternoon window. That is 13 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 365 flights scheduled in it.

Across the year

Delta on MDW to ATL through the year

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

July is the worst month at 75.6% on time, 19 points below November, the best at 95.0%. 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 138 flights.

Across the week, Thursday is the strongest day at 89.7% on time and Sunday the weakest at 82.2%. 8 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Delta runs late on this route

One category carries most of the weight here. Carrier accounts for 57% of the 16,000 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.

Carrier
57%
Late-arriving aircraft
29%
National Airspace System
10%
Extreme weather
4%

The largest share of delay minutes, 57%, 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 9,336 of the 16,000 delay minutes reported here. The split is drawn from 16,390 reported delay minutes.

The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 91.5% on time here.

Cancellations run at 2.53%, against 1.81% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here costs

5.5% 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 an hour and a half, which a normal layover absorbs.

The 591 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 81.5% on time across 1,383 flights, 5 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 5 points of difference.

The sample behind these figures is 1,383 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 Delta on MDW to ATL

Put together: the calendar is the biggest lever here, not the carrier or the hour. November runs 95.0% on time and July 75.6%, a swing of 19 points. If the dates move at all, move them out of July before you think about anything else. 1,343 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