Best Time to Fly ATL to ONT: On-Time Stats by Hour & Airline
Hartsfield-Jackson Atlanta International → Ontario International
Data through July 2026 · Last updated October 18, 2026
937 flights were scheduled from Atlanta (ATL) to Ontario (ONT) in the last 12 months, and 75.3% of those that flew arrived on time, 2.3 points below the US average of 77.6%.
Delta Air Lines was the only reporting airline with regular flights on this route.
Over 24 months, Wednesday was the most reliable day (82% on time) and July the worst month (66%).
The cancellation rate was 1.7% (US average 1.8%).
ATL to ONT 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 |
|---|---|---|---|---|
| Delta Air Lines | 75.3% | 51 min | 1.7% | 937 |
80%+ good 70–79.9% fair <70% poor
Best time of day to fly ATL to ONT
On-time arrival % by scheduled departure hour (local time), 1,865 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 8am–9am | 93.1% | 1.7% | 177 |
| 9am–10am | 85.7% | 1.4% | 505 |
| 10am–11am | 73.9% | 2.1% | 48 |
| 4pm–5pm | 58.8% | 0.0% | 85 |
| 5pm–6pm | 74.3% | 1.1% | 287 |
| 6pm–7pm | 73.7% | 2.0% | 101 |
| 7pm–8pm | 78.2% | 0.8% | 134 |
| 8pm–9pm | 67.5% | 2.0% | 306 |
| 9pm–10pm | 63.6% | 0.5% | 222 |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on ATL to ONT
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) | 63.2% | -15.6 pts | 0.0% | 38 |
| Christmas & New Year (Dec 20 - Jan 3) | 76.6% | -2.1 pts | 4.9% | 82 |
| Summer peak (Jun 15 - Aug 15) | 67.9% | -10.8 pts | 1.7% | 349 |
| All other days | 78.7% | — | 1.0% | 1,396 |
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).