Atlanta (ATL) to Ontario (ONT): On-Time Performance
Data through May 2026
Atlanta (ATL) to Ontario (ONT) effectively runs on two schedules. In October 2024, 95% of arrivals were on time; in July 2024 that fell to 56% — a 39-point seasonal swing. Across the full period the route averages 77% on-time against a national 78%. Morning departures also hold up better than evening ones (87% vs 70%), which matters most in the rough months.
- On-time
- 77%
- arrived <15 min late
- Avg delay
- 14 min
- completed flights
- Cancelled
- 1.6%
- Flights/day
- 2.6
- last 12 months
- Duration
- 4h 35m
- scheduled
- Distance
- 1,900 mi
Monthly on-time trend
Best time to fly from ATL to ONT
Aim for departures around 8 a.m. (92% on-time); avoid 4 p.m. departures (53%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 74% | 15 min |
| Tuesday | 77% | 12 min |
| Wednesdaybest | 79% | 11 min |
| Thursday | 78% | 11 min |
| Friday | 77% | 15 min |
| Saturday | 77% | 16 min |
| Sunday | 74% | 19 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft25%
- Airline operations49%
- National airspace system20%
- Weather6%
Frequently asked questions
- How often are flights from ATL to ONT delayed?
- 24% of ATL–ONT flights arrived 15 or more minutes late (the US DOT definition of a delay) between 2024-06 and 2026-05. The average arrival delay across completed flights was 14 minutes.
- What is the best time of day to fly from ATL to ONT?
- Departures around 8 a.m. have the best record (92% on-time), while departures around 4 p.m. have the worst (53%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from ATL to ONT?
- The scheduled ATL–ONT flight time averages 4h 35m over 1,900 miles. Actual arrival times vary — flights on this route land 15+ minutes late 24% of the time.
- How often are ATL to ONT flights cancelled?
- 1.6% of scheduled flights on this route were cancelled between 2024-06 and 2026-05, at or below the national rate of 1.6%.
- What is the worst month to fly from ATL to ONT?
- July 2024 was the roughest month in this dataset, with only 56% of arrivals on time. The best was October 2024 at 95%. If your dates are flexible, that 39-point gap is worth planning around.
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Based on 1,866 flights, 2024-06–2026-05. Source: US DOT Bureau of Transportation Statistics. Updated 2026-07-01.