Carrier route record
UAATL→ORD
United Airlines · Atlanta to Chicago
- 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 ATL to ORD 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 an hour and a half behind schedule. That rests on 1,611 flights. The strongest carrier on the route with a full sample, American Airlines, flew 688 at 72.2% on time.
The US average over the same twelve months is 77.6%, so there is little to separate United on ATL to ORD from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
74.3%
Arrivals under 15 minutes late, of 1,578 completed flights
Avg delay
92 min
Across delayed arrivals only, not all flights
Cancelled
1.55%
National rate is 1.81%
Whole route
70.6%
Every carrier on ATL to ORD, 6,406 flights
These figures cover 1,611 flights between July 2025 and June 2026. Beyond the headline rate, 10.3% 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 ATL to ORD
United flew 1,611 of the 6,406 flights on ATL to ORD, about 25% of it. Its 74.3% on time is 4 points better than the route as a whole, which runs 70.6%. Ranked by on-time rate it is number four of nine carriers on the route, where the range runs from PSA at 100.0% to Frontier at 62.8%. Five of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The choice of carrier is not cosmetic here. American Airlines arrives on time 72.2% of the time; Frontier Airlines manages 62.8%. Sample sizes sit next to every figure, because a two-point gap across 711 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| PSA Airlinesthin sample | 5 | 100.0% | — | 0.00% | A+ |
| SkyWest Airlinesthin sample | 40 | 84.2% | 88 min | 5.00% | B− |
| Spirit Airlinesthin sample | 75 | 83.8% | 38 min | 0.00% | B+ |
| United Airlines (this page) | 1,611 | 74.3% | 92 min | 1.55% | C |
| Republic Airwaysthin sample | 287 | 72.4% | 65 min | 5.92% | C− |
| American Airlines | 688 | 72.2% | 98 min | 3.05% | C− |
| Envoy Airthin sample | 364 | 71.3% | 83 min | 2.20% | C |
| Delta Air Lines | 2,625 | 69.1% | 63 min | 2.21% | C |
| Frontier Airlines | 711 | 62.8% | 111 min | 2.67% | D |
American Airlines cancels 3.0% 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 ATL to ORD
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 28 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am—
- 8am–11am513 flights82.4%
- 11am–2pm345 flights81.1%
- 2pm–5pm364 flights72.9%
- 5pm–8pm355 flights59.1%
- 8pm–5am34 flights54.5%
Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 54.5% on time, against 82.4% 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 8am–11am window is the busiest, with 513 flights scheduled in it.
Across the year
United on ATL to ORD through the year
July is the worst month at 63.0% on time, 24 points below September, the best at 87.0%. 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 78.2% on time and Monday the weakest at 68.8%. 9 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. National Airspace System accounts for 45% of the 37,000 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.
- 45%National Airspace System
- 28%Late-arriving aircraft
- 21%Carrier
- 6%Extreme weather
45% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 17,000 minutes out of 37,000, against a national NAS share of 21%. The split is drawn from 37,176 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 82.4% on time here.
Cancellations sit at 1.55% against a national 1.81%, which is ordinary. Diversions add another 0.50%.
Connections and stage length
What a delay here costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.3% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
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 74.7% 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 ATL to ORD
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 87.0% on time and July 63.0%, a swing of 24 points. If the dates move at all, move them out of July before you think about anything else. 1,578 completed flights over 12 months sit behind that.
Related
Where to go next
- ATL to ORD, every carrier
- United on ORD to ATL, the return leg
- Republic Airways on ATL to ORD72.4%
- American Airlines on ATL to ORD72.2%
- Envoy Air on ATL to ORD71.3%
- Delta Air Lines on ATL to ORD69.1%
- Frontier Airlines on ATL to ORD62.8%
- United Airlines network-wide record
- Hartsfield-Jackson Atlanta International (ATL) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- How often a connection fails at the major US hubs
- The best time of day to fly, according to 7.04 million flight records
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.