Carrier route record
UAORD→ATL
United Airlines · Chicago to Atlanta
- Flights
- 1,611
- Period
- July 2025 to June 2026
- Share of route
- 25%
- Carriers
- 9
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on ORD to ATL sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 1,611 flights. The strongest carrier on the route with a full sample, Delta Air Lines, flew 2,623 at 80.4% on time.
Delta Air Lines is the most reliable of the four carriers covered here at 80.4% on time across 2,623 flights.
Key figures
On time
74.7%
Arrivals under 15 minutes late, of 1,591 completed flights
Avg delay
68 min
Across delayed arrivals only, not all flights
Cancelled
1.12%
National rate is 1.81%
Whole route
75.0%
Every carrier on ORD to ATL, 6,409 flights
These figures cover 1,611 flights between July 2025 and June 2026. Beyond the headline rate, 8.6% 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
United against every carrier on ORD to ATL
United flew 1,611 of the 6,409 flights on ORD to ATL, about 25% of it. Its 74.7% on time is about level with the route as a whole at 75.0%. Ranked by on-time rate it is number four of nine carriers on the route, where the range runs from Delta at 80.4% to Spirit at 60.0%. Four of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. Delta Air Lines arrives on time 80.4% of the time; American Airlines manages 65.3%. Sample sizes sit next to every figure, because a two-point gap across 689 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Lines | 2,623 | 80.4% | 87 min | 2.36% | B |
| PSA Airlinesthin sample | 5 | 80.0% | 58 min | 0.00% | B+ |
| Envoy Air | 366 | 77.7% | 62 min | 2.19% | B |
| United Airlines (this page) | 1,611 | 74.7% | 68 min | 1.12% | C |
| Republic Airwaysthin sample | 287 | 72.1% | 63 min | 4.53% | C− |
| Frontier Airlines | 713 | 67.8% | 100 min | 3.09% | C− |
| American Airlines | 689 | 65.3% | 86 min | 3.05% | C− |
| SkyWest Airlinesthin sample | 40 | 61.5% | 93 min | 2.50% | D |
| Spirit Airlinesthin sample | 75 | 60.0% | 74 min | 0.00% | D+ |
Frontier Airlines cancels 3.1% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
Flight by flight
United flight numbers on ORD to ATL
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 33 points, against 15 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am280 flights86.6%
- 8am–11am577 flights82.1%
- 11am–2pm—
- 2pm–5pm358 flights74.2%
- 5pm–8pm361 flights53.6%
- 8pm–5am35 flights79.4%
Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 53.6% on time, against 86.6% 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 8am–11am window is the busiest, with 577 flights scheduled in it.
Across the year
United on ORD to ATL through the year
July is the worst month at 61.5% on time, 28 points below September, the best at 89.0%. 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. June was the busiest month here, with 173 flights.
Across the week, Tuesday is the strongest day at 81.2% on time and Sunday the weakest at 67.7%. 14 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
One category carries most of the weight here. Late-arriving aircraft accounts for 47% of the 27,000 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.
- 47%Late-arriving aircraft
- 25%Carrier
- 22%National Airspace System
- 7%Extreme weather
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 27,000 reported delay minutes here, that single category outweighs weather by 7 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 27,384 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 86.6% on time here.
Cancellations sit at 1.12% against a national 1.81%, which is ordinary. Diversions add another 0.12%.
Connections and stage length
What a delay here costs
8.6% 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 a little over an hour, which a normal layover absorbs.
The 606 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 74.3% on time across 1,611 flights, within half a point 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 1,611 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 United on ORD to ATL
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 89.0% on time and July 61.5%, a swing of 28 points. If the dates move at all, move them out of July before you think about anything else. 1,591 completed flights over 12 months sit behind that.
Related
Where to go next
- ORD to ATL, every carrier
- United on ATL to ORD, the return leg
- Delta Air Lines on ORD to ATL80.4%
- Envoy Air on ORD to ATL77.7%
- Republic Airways on ORD to ATL72.1%
- Frontier Airlines on ORD to ATL67.8%
- American Airlines on ORD to ATL65.3%
- United Airlines network-wide record
- Chicago O'Hare International (ORD) delay statistics
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
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.