Best Time to Fly STL to MDW: On-Time Stats by Hour & Airline
St Louis Lambert International → Chicago Midway International
Data through July 2026 · Last updated October 18, 2026
Over the last 12 months, 80.0% of St. Louis (STL) to Chicago (MDW) flights arrived on time (1,704 scheduled flights). That is 2.4 points above the national average of 77.6%.
Southwest Airlines was the only reporting airline with regular flights on this route.
Over 24 months, Tuesday was the most reliable day (89% on time) and July the worst month (70%).
The cancellation rate was 1.2% (US average 1.8%).
STL to MDW on-time performance by airline
Last 12 months. Airlines with fewer than 30 completed flights are marked “limited data”.
| Airline | On time | Avg delay when late | Cancelled | Flights |
|---|---|---|---|---|
| Southwest Airlines | 80.0% | 52 min | 1.2% | 1,704 |
80%+ good 70–79.9% fair <70% poor
Best time of day to fly STL to MDW
On-time arrival % by scheduled departure hour (local time), 3,524 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 5am–6am | 94.3% | 1.1% | 374 |
| 6am–7am | 95.5% | 1.0% | 203 |
| 7am–8am | 87.0% | 1.3% | 227 |
| 8am–9am | 92.5% | 0.5% | 202 |
| 9am–10am | 89.6% | 0.0% | 106 |
| 10am–11am | 89.6% | 2.6% | 227 |
| 11am–12pm | 80.7% | 1.1% | 175 |
| 12pm–1pm | 80.9% | 1.1% | 90 |
| 1pm–2pm | 86.3% | 0.5% | 213 |
| 2pm–3pm | 91.6% | 2.2% | 183 |
| 3pm–4pm | 80.8% | 0.6% | 183 |
| 4pm–5pm | 65.7% | 1.6% | 249 |
| 5pm–6pm | 77.1% | 0.6% | 177 |
| 6pm–7pm | 73.6% | 1.7% | 297 |
| 7pm–8pm | 74.5% | 1.4% | 145 |
| 8pm–9pm | 75.9% | 0.4% | 262 |
| 9pm–10pm | 70.9% | 1.2% | 160 |
| 10pm–11pm | 62.8% | 0.0% | 51 |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on STL to MDW
On-time arrivals during holiday periods compared with all other days, last 24 months.
| Period | On time | vs other days | Cancelled | Flights |
|---|---|---|---|---|
| Thanksgiving week (Tue before to Mon after) | 76.7% | -8.6 pts | 4.8% | 63 |
| Christmas & New Year (Dec 20 - Jan 3) | 78.1% | -7.2 pts | 0.0% | 137 |
| Summer peak (Jun 15 - Aug 15) | 73.8% | -11.5 pts | 1.0% | 673 |
| All other days | 85.3% | — | 1.1% | 2,651 |
Monthly on-time trend
On-time arrival % each month, with the 12-month US average for reference.
What causes delays on this route
Share of reported delay minutes, last 12 months (BTS cause categories).