69% of flights from St. Louis to Chicago arrived on time over the past 12 months. That is worse than the typical U.S. route. The 6 a.m. departures ran on time 84% of the time; the 8 p.m. ones 51%. Most reliable airline: American Airlines (71%). 16% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for STL → ORD: when a flight was late, it was under 45 minutes late 46% of the time. About 1 in 8 flights landed an hour or more late, and 1 in 28 three hours or more; 3.2% were cancelled outright.
- On time or early69%
- 15–30 min late8.3%
- 30–60 min late7.0%
- 1–2 hours late5.8%
- 2–3 hours late2.9%
- 3+ hours late3.5%
- Diverted0.2%
- Cancelled3.2%
Share of all 5,247 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| United Airlines | 3,141 | 68% | 2.8% | −2 min | 12.5% | +97 min | GoJet 68%, United Airlines 19%, SkyWest 7%, Republic Airways 6% |
| American Airlines | 2,106 | 71% | 3.9% | −7 min | 11.8% | +108 min | Envoy 40%, SkyWest 27%, American Airlines 22%, Republic Airways 11% |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at STL). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | United Airlines | American Airlines |
|---|---|---|
| 6 a.m. | 84% | 84% |
| 7 a.m. | 77% | 80% |
| 8 a.m. | 76% | 77% |
| 9 a.m. | 69% | 86% |
| 10 a.m. | 71% | — |
| 11 a.m. | 69% | — |
| noon | 70% | — |
| 1 p.m. | 64% | 61% |
| 2 p.m. | — | 67% |
| 3 p.m. | 59% | — |
| 4 p.m. | — | 61% |
| 5 p.m. | 61% | 74% |
| 6 p.m. | 55% | — |
| 7 p.m. | 54% | — |
| 8 p.m. | — | 54% |
Last flight of the day
On STL → ORD, each airline's last flight of the day was cancelled 6.7% of the time, against 2.7% for its earlier flights (2.5× as often). It arrived 3+ hours late 2.5% of the time (earlier flights: 3.7%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| American Airlines | 8:07 p.m. | 7.4% | 1.9% | 3.2% | first flight 6:55 a.m. |
| United Airlines | 7:05 p.m. | 6.0% | 3.0% | 2.3% | first flight 6:00 a.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
If you need to be in ORD tonight, book an earlier flight so there's a backup if it's cancelled.
By month
Each calendar month pooled over 2023–2026. Best: February (83%). Worst: January (66%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 782 | 66% | 6.3% |
| Tuesday | 714 | 74% | 1.8% |
| Wednesday | 753 | 72% | 2.1% |
| Thursday | 761 | 71% | 2.6% |
| Friday | 762 | 67% | 3.4% |
| Saturday | 700 | 71% | 3.0% |
| Sunday | 775 | 64% | 3.1% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 127 · air traffic/airport 39 · airline 3
Month by month
Flight numbers on this route
Regular flights with at least 120 scheduled trips in the past year. Sorted by departure time.
| Flight | Departs | Flights | On time | Cancelled | Typical arrival | Operated by |
|---|---|---|---|---|---|---|
| UA 4423 | 6:30 a.m. | 323 | 84% | 0.6% | −7 min | GoJet |
| UA 4183 | 8:00 a.m. | 211 | 72% | 0.5% | 0 min | GoJet |
| UA 4395 | 11:25 a.m. | 320 | 69% | 2.8% | −2 min | GoJet |
| AA 1926 | 12:27 p.m. | 121 | 76% | 2.5% | −12 min | American Airlines |
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Mar 16, 2026 | 14 | 0% | 3 |
| Dec 7, 2025 | 14 | 0% | 2 |
| Nov 10, 2025 | 14 | 0% | 4 |
| Nov 30, 2025 | 14 | 0% | 0 |
| Nov 29, 2025 | 12 | 0% | 7 |
Nearby airport alternatives
Other ways to make the same trip, using airports within 60 miles of St. Louis or Chicago. STL → MDW has been 9 points more reliable.
| Route | Flights | On time | Cancelled |
|---|---|---|---|
| STL → ORD (this route) | 5,247 | 69% | 3.2% |
| STL → MDW St. Louis Lambert to Chicago Midway | 1,698 | 78% | 1.2% |
Questions
How often are flights from STL to ORD on time?
69% of 5,247 scheduled flights from St. Louis, MO to Chicago, IL arrived within 15 minutes of schedule between September 2025 and August 2026. 3.2% were cancelled.
What is the best time of day to fly STL to ORD?
Flights scheduled to leave at 6 a.m. were the most reliable (84% on time). The 8 p.m. departures were the least (51%).
Which airline is most on time from STL to ORD?
American Airlines: 71% of its 2,106 flights on the route arrived on time. United Airlines: 68%.
What month has the most delays from STL to ORD?
January (66% on time). The best month is February (83%), over 2023–2026.
Is the last flight of the day from STL to ORD more likely to be cancelled?
Yes. Each airline's last STL–ORD flight of the day was cancelled 6.7% of the time over the past year, against 2.7% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- ORD → STL (return)
- St. Louis Lambert (STL) delays by hour
- Flights into Chicago O'Hare (ORD)
- United Airlines on-time record
- American Airlines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.