Denver (DEN) to Ontario (ONT): On-Time Performance
Data through May 2026
When you fly DEN to ONT matters as much as anything else about the booking: the route swung from 89% on-time in October 2024 to just 59% in July 2025. Across the full period the route averages 75% on-time against a national 78%. Morning departures also hold up better than evening ones (87% vs 66%), which matters most in the rough months.
- On-time
- 75%
- arrived <15 min late
- Avg delay
- 15 min
- completed flights
- Cancelled
- 0.4%
- Flights/day
- 7.3
- last 12 months
- Duration
- 2h 22m
- scheduled
- Distance
- 819 mi
Best airline from DEN to ONT
3 airlines flew this route regularly between 2024-06 and 2026-05.
| Airline | On-time | Avg delay | Cancelled | Flights |
|---|---|---|---|---|
| Frontier Airlinesmost reliable | 79% | 14 min | 0.7% | 1,214 |
| United Airlines | 79% | 16 min | 0.3% | 1,779 |
| Southwest Airlines | 72% | 15 min | 0.4% | 2,563 |
Monthly on-time trend
Best time to fly from DEN to ONT
Aim for departures around 10 a.m. (94% on-time); avoid 6 p.m. departures (58%).
By day of week
| Day | On-time | Avg delay |
|---|---|---|
| Monday | 71% | 17 min |
| Tuesdaybest | 78% | 14 min |
| Wednesdaybest | 78% | 14 min |
| Thursday | 76% | 16 min |
| Friday | 75% | 14 min |
| Saturday | 76% | 14 min |
| Sunday | 74% | 16 min |
What causes delays on this route
Share of total delay minutes by cause, as reported by carriers to the US DOT.
- Late-arriving aircraft54%
- Airline operations35%
- National airspace system10%
- Weather1%
Frequently asked questions
- How often are flights from DEN to ONT delayed?
- 25% of DEN–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 15 minutes.
- Which airline is most reliable from DEN to ONT?
- Frontier Airlines has the best on-time record on this route at 79%, based on 1,214 flights. 3 airlines flew DEN–ONT frequently enough to compare in this period.
- What is the best time of day to fly from DEN to ONT?
- Departures around 10 a.m. have the best record (94% on-time), while departures around 6 p.m. have the worst (58%). As on most US routes, delays accumulate through the day, so earlier flights are generally safer.
- How long is the flight from DEN to ONT?
- The scheduled DEN–ONT flight time averages 2h 22m over 819 miles. Actual arrival times vary — flights on this route land 15+ minutes late 25% of the time.
- How often are DEN to ONT flights cancelled?
- 0.4% 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 DEN to ONT?
- July 2025 was the roughest month in this dataset, with only 59% of arrivals on time. The best was October 2024 at 89%. If your dates are flexible, that 31-point gap is worth planning around.
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Based on 5,562 flights, 2024-06–2026-05. Source: US DOT Bureau of Transportation Statistics. Updated 2026-07-01.