Route reliability record
STL→ORD
St. Louis to Chicago
- Flights
- 3,112
- Period
- September 2025 to August 2026
- Distance
- 258 mi
- Carriers
- 5
This route carries a cancellation problem, not just a delay problem: 3.5% of scheduled flights never operate, against 1.9% 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 3,112 STL to ORD flights, of which American Airlines flew 470 at 82.0% on time.
Best time to fly STL to ORD: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 84.7% of the time and Saturday flights 76.5%, against 72.5% for the route overall.
American Airlines is the most reliable of the five carriers covered here at 82.0% on time across 470 flights.
Key figures
On time
72.5%
Arrivals under 15 minutes late, of 2,998 completed flights
Avg delay
102 min
Across delayed arrivals only, not all flights
Cancelled
3.50%
National rate is 1.89%
Best carrier
American
82.0% on time across 470 flights
These figures cover 3,112 flights between September 2025 and August 2026. Beyond the headline rate, 12.2% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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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 82.0% of the time; SkyWest Airlines manages 64.2%. Sample sizes sit next to every figure, because a two-point gap across 783 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| American Airlines | 470 | 82.0% | 141 min | 2.77% | B |
| Envoy Air | 844 | 75.2% | 95 min | 3.32% | B− |
| Republic Airways | 415 | 74.2% | 78 min | 4.58% | C− |
| United Airlines | 600 | 70.9% | 91 min | 1.67% | C |
| SkyWest Airlines | 783 | 64.2% | 110 min | 4.98% | D− |
SkyWest Airlines cancels 5.0% 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.
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Best ways to make this trip
The most reliable ways to fly St. Louis to Chicago
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 1 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. STL → ORDSt. Louis to Chicago | American Airlines | 79.7% | 82.0% | 2.77% | 5am–8am, Wed | — |
| 2. STL → MDWSt. Louis to Chicago | Southwest Airlines | 78.6% | 79.5% | 1.18% | 5am–8am, Tue | — |
| 3. STL → ORDSt. Louis to Chicago | Envoy Air | 72.7% | 75.2% | 3.32% | 5am–8am, Sat | — |
| 4. STL → ORDSt. Louis to Chicago | Republic Airways | 70.8% | 74.2% | 4.58% | 5am–8am, Thu | — |
| 5. STL → ORDSt. Louis to Chicago | United Airlines | 69.7% | 70.9% | 1.67% | 5am–8am, Mon | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
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 25 points, against 18 points between the best and worst carrier.
- 5am–8am642 flights84.7%
- 8am–11am567 flights80.1%
- 11am–2pm387 flights65.5%
- 2pm–5pm650 flights69.9%
- 5pm–8pm643 flights64.6%
- 8pm–5am223 flights59.6%
Scale runs 50% to 90%.
The 8pm–5am window is where this operation falls apart: 59.6% on time, against 84.7% 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 650 flights scheduled in it.
Explore
Filter STL to ORD by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On STL to ORD, the best departure window is 5am–8am at 84.7% on time and the worst is 8pm–5am at 59.6%, a wide gap of 25.1 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am84.7%
- 8–11am80.1%
- 11am–2pm65.5%
- 2–5pm69.9%
- 5–8pm64.6%
- 8pm–5am59.6%
best all US flightsScale 50% to 95%.
Across the year
When delays peak on this route
This route's year swings by 21 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.
December is the weak month at 62.7% on time, against 83.7% in February. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. May was the busiest month here, with 322 flights.
Across the week, Saturday is the strongest day at 76.5% on time and Sunday the weakest at 65.9%, a spread of 11 points.
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 84,000 reported delay minutes.
- 36%National Airspace System
- 31%Late-arriving aircraft
- 22%Carrier
- 11%Extreme weather
- 0%Security
36% 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 30,000 minutes out of 84,000, against a national NAS share of 21%. The split is drawn from 83,501 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 84.7% on time here.
Cancellations run at 3.50%, against 1.89% 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
12.2% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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 71.2% on time across 3,113 flights, within about 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 3,112 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.
Work out the risk of missing a connection in ORD after this flight
What to do with this
Booking this route
Put together: the delay figures matter less here than the 3.50% cancellation rate. A late arrival costs you close to two hours; 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. 2,998 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 four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.5% of the 3,112 flights in this analysis, against 22.7% nationally. Delayed flights are late by close to two hours on average.
Which airline is most reliable on STL to ORD?
American Airlines leads at 82.0% on time across 470 flights. SkyWest Airlines is at the other end on 64.2%, 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 84.7% on time. The 8pm–5am window is the weakest at 59.6%, 25 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 December delays on STL to ORD?
December is the weakest month at 62.7% on time, compared with 83.7% in February. Across the year that is 21 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- ORD to STL — the return legseparate record
- St. Louis Lambert International (STL) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- American Airlines on STL to ORD82.0%
- Envoy Air on STL to ORD75.2%
- Republic Airways on STL to ORD74.2%
- United Airlines on STL to ORD70.9%
- SkyWest Airlines on STL to ORD64.2%
- STL to DEN, a related route75.0%
- LGA to ORD, a related route66.7%
- STL to ATL, a related route84.6%
- American Airlines on-time record82.0%
- Envoy Air on-time record75.2%
- Republic Airways on-time record74.2%
- The US routes with the most cancellations
- Same route, different airline: where the carrier you pick matters most
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.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.