Carrier route record

DLATL→MDW

Delta Air Lines · Atlanta to Chicago

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 ATL to MDW lands a B, 4 points better than the national rate of 77.6%. Roughly 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 1,383 flights. The strongest carrier on the route with a full sample, Southwest Airlines, flew 1,545 at 75.9% on time.

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

On time

81.5%

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

Avg delay

58 min

Across delayed arrivals only, not all flights

Cancelled

2.24%

National rate is 1.81%

Whole route

76.3%

Every carrier on ATL to MDW, 3,527 flights

These figures cover 1,383 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

Delta against every carrier on ATL to MDW

Delta flew 1,383 of the 3,527 flights on ATL to MDW, about 39% of it. Its 81.5% on time is 5 points better than the route as a whole, which runs 76.3%. Ranked by on-time rate it is first of three carriers on the route, where the range runs from Delta at 81.5% to Frontier at 65.2%.

The choice of carrier is not cosmetic here. Southwest Airlines arrives on time 75.9% of the time; Frontier Airlines manages 65.2%. Sample sizes sit next to every figure, because a two-point gap across 599 flights means less than a ten-point one.

On-time performance by carrier on ATL to MDW
Airline	Flights	On time	Avg delay	Cancelled	Grade
Delta Air Lines (this page)	1,383	81.5%	58 min	2.24%	B
Southwest Airlines	1,545	75.9%	55 min	1.62%	B
Frontier Airlines	599	65.2%	97 min	1.50%	C

Southwest leads Frontier by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Flight by flight

Delta flight numbers on ATL to MDW

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 24 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am—
8am–11am365 flights86.7%
11am–2pm281 flights87.4%
2pm–5pm333 flights79.4%
5pm–8pm39 flights63.2%
8pm–5am365 flights75.8%

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

The 5pm–8pm window is where this operation falls apart: 63.2% on time, against 87.4% for the 11am–2pm 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 8am–11am window is the busiest, with 365 flights scheduled in it.

Across the year

Delta on ATL to MDW through the year

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

July is the worst month at 68.4% on time, 22 points below September, the best at 90.7%. 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, Tuesday is the strongest day at 87.0% on time and Monday the weakest at 76.6%. 10 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 45% of the 14,000 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
45%
Late-arriving aircraft
25%
National Airspace System
16%
Extreme weather
14%
Security
0%

Extreme weather accounts for 14% of delay minutes, well above the single-digit share typical across the system. Weather delays are lumpy: they arrive as whole bad days rather than as a steady drag, so the monthly strip above is the more useful view of the risk. The national share is 6%, so this operation carries roughly 2.3 times the usual weather exposure. The split is drawn from 14,340 reported delay minutes.

The largest share of delay minutes, 45%, 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 6,452 of the 14,000 delay minutes reported here.

Cancellations sit at 2.24% against a national 1.81%, which is ordinary. Diversions add another 0.65%.

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 about an hour, 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 86.9% on time across 1,383 flights, 5 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 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 ATL to MDW

Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 90.7% on time and July 68.4%, a swing of 22 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