Carrier route record
UASTL→ORD
United Airlines · St. Louis to Chicago
- Flights
- 525
- Period
- July 2025 to June 2026
- Share of route
- 17%
- Carriers
- 5
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on STL to ORD sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land an hour and a half behind schedule. That rests on 525 flights. The strongest carrier on the route with a full sample, American Airlines, flew 533 at 80.7% on time.
American Airlines is the most reliable of the four carriers covered here at 80.7% on time across 533 flights.
Key figures
On time
68.6%
Arrivals under 15 minutes late, of 516 completed flights
Avg delay
85 min
Across delayed arrivals only, not all flights
Cancelled
1.52%
National rate is 1.81%
Whole route
71.1%
Every carrier on STL to ORD, 3,070 flights
These figures cover 525 flights between July 2025 and June 2026. Beyond the headline rate, 9.7% 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 STL to ORD
United flew 525 of the 3,070 flights on STL to ORD, about 17% of it. Its 68.6% on time is 3 points worse than the route as a whole, which runs 71.1%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from American at 80.7% to SkyWest at 62.8%.
The choice of carrier is not cosmetic here. American Airlines arrives on time 80.7% of the time; SkyWest Airlines manages 62.8%. Sample sizes sit next to every figure, because a two-point gap across 836 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlines | 533 | 80.7% | 126 min | 2.44% | B |
| Envoy Air | 728 | 74.6% | 93 min | 2.61% | C |
| Republic Airways | 448 | 72.0% | 76 min | 4.02% | C− |
| United Airlines (this page) | 525 | 68.6% | 85 min | 1.52% | C |
| SkyWest Airlines | 836 | 62.8% | 104 min | 4.90% | D− |
SkyWest Airlines cancels 4.9% 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.
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 22 points, against 18 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am137 flights79.1%
- 8am–11am49 flights62.5%
- 11am–2pm72 flights80.0%
- 2pm–5pm59 flights72.9%
- 5pm–8pm208 flights58.0%
- 8pm–5am—
Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 58.0% on time, against 80.0% 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 5pm–8pm window is the busiest, with 208 flights scheduled in it.
Across the year
United on STL to ORD through the year
- Jul–Sep 2025175 flights62.2%
- Oct–Dec 2025131 flights65.6%
- Jan–Mar 202647 flights69.6%
- Apr–Jun 2026172 flights77.2%
Scale runs 55% to 85%. Rows with fewer than 30 flights show a dash.
Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 68.6% on time across 525 flights.
United on STL to ORD did not run the same all year. Its best quarter was Apr–Jun 2026 at 77.2% on time and its weakest Jul–Sep 2025 at 62.2%, a swing of 15 points on roughly 131 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.
Across the week, Monday is the strongest day at 76.4% on time and Sunday the weakest at 62.5%. 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. National Airspace System accounts for 61% 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.
- 61%National Airspace System
- 23%Carrier
- 13%Late-arriving aircraft
- 3%Extreme weather
61% 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 8,407 minutes out of 14,000, against a national NAS share of 21%. The split is drawn from 13,714 reported delay minutes.
Cancellations sit at 1.52% against a national 1.81%, which is ordinary. Diversions add another 0.19%.
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. 9.7% 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.
At 258 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 11am–2pm window matters as much as it does.
The return leg runs 71.2% on time across 528 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
One caution: this is a thin sample. 525 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking United on STL to ORD
Put together: treat all of this as provisional. 525 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 68.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 516 completed flights over 12 months sit behind that.
Related
Where to go next
- STL to ORD, every carrier
- United on ORD to STL, the return leg
- American Airlines on STL to ORD80.7%
- Envoy Air on STL to ORD74.6%
- Republic Airways on STL to ORD72.0%
- SkyWest Airlines on STL to ORD62.8%
- United Airlines network-wide record
- St. Louis Lambert International (STL) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- Same route, different airline: where the carrier you pick matters most
- How often a connection fails at the major US hubs
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.