Route reliability record

STL→ORD

St. Louis to Chicago

Flights: 3,070
Period: July 2025 to June 2026
Distance: 258 mi
Carriers: 5

This route carries a cancellation problem, not just a delay problem: 3.2% of scheduled flights never operate, against 1.8% nationally. Of the ones that do fly, about seven flights in ten arrive on time, worth a C− overall. The punctuality figure counts only flights that actually departed, so it flatters an operation that cancels this often. That rests on 3,070 flights, of which American Airlines flew 533 at 80.7% on time.

American Airlines is the most reliable of the five carriers covered here at 80.7% on time across 533 flights.

On time

71.1%

Arrivals under 15 minutes late, of 2,967 completed flights

Avg delay

97 min

Across delayed arrivals only, not all flights

Cancelled

3.22%

National rate is 1.81%

Best carrier

American

80.7% on time across 533 flights

These figures cover 3,070 flights between July 2025 and June 2026. Beyond the headline rate, 12.0% 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

Which airline is most reliable on STL to ORD

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.

On-time performance by carrier on STL to ORD
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	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

The best time of day to leave

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 31 points, against 18 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am661 flights83.3%
8am–11am529 flights77.1%
11am–2pm360 flights65.8%
2pm–5pm700 flights70.0%
5pm–8pm610 flights62.9%
8pm–5am210 flights52.8%

Scale runs 45% to 90%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 52.8% on time, against 83.3% 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 2pm–5pm window is the busiest, with 700 flights scheduled in it.

Across the year

When delays peak on this route

This route's year swings by 22 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.

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

July is the worst month at 61.3% on time, 22 points below February, the best at 83.7%. 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. May was the busiest month here, with 322 flights.

Across the week, Saturday is the strongest day at 74.3% on time and Sunday the weakest at 66.4%. 8 points is a smaller lever than departure hour, but it is free.

Delay causes

Why this route gets delayed

Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 83,000 reported delay minutes.

National Airspace System
32%
Late-arriving aircraft
29%
Carrier
29%
Extreme weather
10%
Security
0%

32% 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 27,000 minutes out of 83,000, against a national NAS share of 21%. The split is drawn from 82,778 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 83.3% on time here.

Cancellations run at 3.22%, against 1.81% nationally. That is about one flight in 30 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.

Connections and stage length

What a delay here actually costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 12.0% 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 5am–8am window matters as much as it does.

The return leg runs 71.0% on time across 3,068 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 3,070 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 this route

Put together: the delay figures matter less here than the 3.22% cancellation rate. A late arrival costs you an hour and a half; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 2,967 completed flights over 12 months sit behind that.

Common questions

STL to ORD questions

How often is STL to ORD delayed?

Roughly one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 28.9% of the 3,070 flights in this analysis, against 22.4% nationally. Delayed flights are late by an hour and a half on average.

Which airline is most reliable on STL to ORD?

American Airlines leads at 80.7% on time across 533 flights. SkyWest Airlines is at the other end on 62.8%, a gap of 18 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.

What time of day has the fewest delays on STL to ORD?

The 5am–8am departure window is the strongest at 83.3% on time. The 8pm–5am window is the weakest at 52.8%, 31 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.

How bad are July delays on STL to ORD?

July is the weakest month at 61.3% on time, compared with 83.7% in February. Across the year that is 22 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.

Where to go next

Direction matters. STL to ORD and ORD to STL are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.

Key figures