Carrier route record

UAORD→STL

United Airlines · Chicago to St. Louis

Flights: 528
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 ORD to STL sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 6 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 528 flights. The strongest carrier on the route with a full sample, Republic Airways, flew 444 at 76.2% on time.

Republic Airways is the most reliable of the four carriers covered here at 76.2% on time across 444 flights.

On time

71.2%

Arrivals under 15 minutes late, of 521 completed flights

Avg delay

79 min

Across delayed arrivals only, not all flights

Cancelled

1.33%

National rate is 1.81%

Whole route

71.0%

Every carrier on ORD to STL, 3,068 flights

These figures cover 528 flights between July 2025 and June 2026. Beyond the headline rate, 12.5% 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 STL

United flew 528 of the 3,068 flights on ORD to STL, about 17% of it. Its 71.2% on time is about level with the route as a whole at 71.0%. Ranked by on-time rate it is number three of five carriers on the route, where the range runs from Republic at 76.2% to American at 65.6%.

The choice of carrier is not cosmetic here. Republic Airways arrives on time 76.2% of the time; American Airlines manages 65.6%. Sample sizes sit next to every figure, because a two-point gap across 535 flights means less than a ten-point one.

On-time performance by carrier on ORD to STL
Airline	Flights	On time	Avg delay	Cancelled	Grade
Republic Airways	444	76.2%	77 min	2.48%	B
Envoy Air	727	75.0%	52 min	2.34%	B
United Airlines (this page)	528	71.2%	79 min	1.33%	C
SkyWest Airlines	834	68.2%	73 min	4.20%	C−
American Airlines	535	65.6%	86 min	2.62%	C

SkyWest Airlines cancels 4.2% 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 36 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–11am72 flights84.5%
11am–2pm59 flights91.5%
2pm–5pm210 flights70.8%
5pm–8pm96 flights64.5%
8pm–5am91 flights55.1%

Scale runs 45% to 95%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 55.1% on time, against 91.5% 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 2pm–5pm window is the busiest, with 210 flights scheduled in it.

Across the year

United on ORD to STL through the year

Jul–Sep 2025175 flights69.8%
Oct–Dec 2025132 flights77.3%
Jan–Mar 202648 flights61.7%
Apr–Jun 2026173 flights70.6%

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 71.2% on time across 528 flights.

United on ORD to STL did not run the same all year. Its best quarter was Oct–Dec 2025 at 77.3% on time and its weakest Jan–Mar 2026 at 61.7%, a swing of 16 points on roughly 132 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, Thursday is the strongest day at 78.7% on time and Sunday the weakest at 59.7%. 19 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 50% of the 12,000 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.

Late-arriving aircraft
50%
Carrier
30%
National Airspace System
11%
Extreme weather
8%

50% 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 12,000 reported delay minutes here, that single category outweighs weather by 6 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 11,884 reported delay minutes.

Cancellations sit at 1.33% against a national 1.81%, which is ordinary. Diversions add another 0.00%.

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. 12.5% 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 68.6% on time across 525 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. 528 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 ORD to STL

Put together: treat all of this as provisional. 528 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 71.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 521 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