Best Time to Fly ONT to MDW: On-Time Stats by Hour & Airline
Ontario International → Chicago Midway International
Data through July 2026 · Last updated October 18, 2026
Over the last 12 months, 90.2% of Ontario (ONT) to Chicago (MDW) flights arrived on time (360 scheduled flights). That is 12.6 points above the national average of 77.6%.
Southwest Airlines was the only reporting airline with regular flights on this route.
Over 24 months, Sunday was the most reliable day (93% on time) and June the worst month (82%).
The cancellation rate was 0.3% (US average 1.8%).
ONT 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 | 90.2% | 38 min | 0.3% | 360 |
80%+ good 70–79.9% fair <70% poor
Best time of day to fly ONT to MDW
On-time arrival % by scheduled departure hour (local time), 723 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 5am–6am | 88.3% | 0.0% | 78 |
| 6am–7am | 94.7% | 0.0% | 187 |
| 7am–8am | 92.3% | 0.0% | 39 |
| 8am–9am | 88.7% | 1.0% | 98 |
| 9am–10am | Limited data | 4 | |
| 10am–11am | Limited data | 28 | |
| 11am–12pm | 87.3% | 0.9% | 112 |
| 12pm–1pm | Limited data | 9 | |
| 1pm–2pm | Limited data | 12 | |
| 2pm–3pm | Limited data | 7 | |
| 11pm–12am | 87.8% | 0.0% | 149 |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on ONT 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) | Limited data | 14 | ||
| Christmas & New Year (Dec 20 - Jan 3) | 83.3% | -7.6 pts | 0.0% | 30 |
| Summer peak (Jun 15 - Aug 15) | 84.7% | -6.2 pts | 0.0% | 125 |
| All other days | 90.9% | — | 0.2% | 554 |
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).