75% of flights from Denver to Ontario arrived on time over the past 12 months. That is worse than the typical U.S. route. The 8 a.m. departures ran on time 92% of the time; the 9 p.m. ones 55%. Most reliable airline: Frontier Airlines (80%). 8% of flights arrived more than an hour late or not at all.
How late?
The on-time rate treats a flight 20 minutes late the same as one 5 hours late. Here's the split for DEN → ONT: when a flight was late, it was under 45 minutes late 58% of the time. About 1 in 12 flights landed an hour or more late, and 1 in 114 three hours or more; 0.2% were cancelled outright.
- On time or early75%
- 15–30 min late10%
- 30–60 min late7.2%
- 1–2 hours late5.4%
- 2–3 hours late1.8%
- 3+ hours late0.9%
- Diverted0.0%
- Cancelled0.2%
Share of all 2,623 scheduled flights, past 12 months, by arrival time against schedule.
By airline
| Airline | Flights | On time | Cancelled | Typical arrival | 1h+ late | Avg when late | Operated by |
|---|---|---|---|---|---|---|---|
| Southwest Airlines | 1,269 | 69% | 0.2% | +2 min | 8.2% | +51 min | Southwest Airlines |
| United Airlines | 797 | 79% | 0.0% | −3 min | 8.7% | +68 min | United Airlines |
| Frontier Airlines | 557 | 80% | 0.5% | −9 min | 6.8% | +61 min | Frontier Airlines |
Airline = the name on the ticket. Regional flights (e.g. "Delta Connection") count under the ticketing airline, and the operator is listed.
Best time of day to fly
On-time rate by scheduled departure hour (local time at DEN). Delays build through the day as late planes knock on, so early flights usually do best.
By airline and hour
| Departs | Southwest Airlines | United Airlines | Frontier Airlines |
|---|---|---|---|
| 7 a.m. | 84% | — | — |
| 8 a.m. | 92% | — | 91% |
| 11 a.m. | — | 88% | — |
| 1 p.m. | 79% | — | — |
| 6 p.m. | 50% | — | — |
| 7 p.m. | — | 73% | — |
| 8 p.m. | 59% | — | — |
| 9 p.m. | 52% | — | — |
| 10 p.m. | — | — | 70% |
Last flight of the day
On DEN → ONT, each airline's last flight of the day was cancelled 0.4% of the time, against 0.1% for its earlier flights (6.1× as often). It arrived 3+ hours late 1.1% of the time (earlier flights: 0.9%). It matters more than the numbers suggest. Miss an earlier flight and there's another one that evening; miss the last one and you're usually waiting until morning.
| Airline | Last departure | Last: cancelled | Last: 3h+ late | Earlier: cancelled | Next morning |
|---|---|---|---|---|---|
| Frontier Airlines | 10:29 p.m. | 1.5% | 1.0% | 0.0% | first flight 8:45 a.m. |
| United Airlines | 7:20 p.m. | 0.0% | 1.9% | 0.0% | first flight 11:25 a.m. |
| Southwest Airlines | 8:55 p.m. | 0.3% | 0.3% | 0.1% | first flight 8:15 a.m. |
Last flight = the airline's last scheduled departure on this route that day, on days it flies the route at least twice; past 12 months. Times are typical scheduled times over the latest three months.
If you need to be in ONT tonight, book an earlier flight so there's a backup if it's cancelled.
By month
Each calendar month pooled over 2023–2026. Best: December (81%). Worst: June (60%).
By day of week
| Day | Flights | On time | Cancelled |
|---|---|---|---|
| Monday | 406 | 70% | 0.0% |
| Tuesday | 343 | 79% | 0.3% |
| Wednesday | 348 | 79% | 0.0% |
| Thursday | 399 | 72% | 0.5% |
| Friday | 400 | 74% | 0.5% |
| Saturday | 329 | 76% | 0.0% |
| Sunday | 398 | 74% | 0.0% |
Why flights were late
Share of delay minutes on flights 15+ minutes late, as reported to BTS by the airlines.
Cancellations: weather 3 · airline 1 · air traffic/airport 1
Month by month
Flight numbers on this route
Regular flights with at least 120 scheduled trips in the past year. Sorted by departure time.
| Flight | Departs | Flights | On time | Cancelled | Typical arrival | Operated by |
|---|---|---|---|---|---|---|
| F9 2907 | 8:45 a.m. | 140 | 92% | 0.0% | −12 min | Frontier Airlines |
| UA 430 | 11:15 a.m. | 364 | 88% | 0.0% | −7 min | United Airlines |
| UA 2028 | 7:20 p.m. | 200 | 69% | 0.0% | +2 min | United Airlines |
| F9 1261 | 10:29 p.m. | 270 | 76% | 0.7% | −8 min | Frontier Airlines |
Worst days in the past year
| Date | Flights | On time | Cancelled |
|---|---|---|---|
| Mar 6, 2026 | 7 | 0% | 0 |
| Feb 17, 2026 | 6 | 17% | 0 |
| Dec 3, 2025 | 5 | 20% | 0 |
| Jun 21, 2026 | 9 | 22% | 0 |
| Jun 28, 2026 | 8 | 25% | 0 |
Nearby airport alternatives
Other ways to make the same trip, using airports within 60 miles of Denver or Ontario. DEN → SNA has been 6 points more reliable.
| Route | Flights | On time | Cancelled |
|---|---|---|---|
| DEN → ONT (this route) | 2,623 | 75% | 0.2% |
| DEN → SNA Denver to Orange County John Wayne | 3,710 | 80% | 0.2% |
| DEN → LAX Denver to Los Angeles LAX | 7,708 | 78% | 0.5% |
| DEN → BUR Denver to Hollywood Burbank | 2,128 | 73% | 0.3% |
| DEN → LGB Denver to Long Beach | 1,005 | 72% | 0.6% |
Questions
How often are flights from DEN to ONT on time?
75% of 2,623 scheduled flights from Denver, CO to Ontario, CA arrived within 15 minutes of schedule between September 2025 and August 2026. 0.2% were cancelled.
What is the best time of day to fly DEN to ONT?
Flights scheduled to leave at 8 a.m. were the most reliable (92% on time). The 9 p.m. departures were the least (55%).
Which airline is most on time from DEN to ONT?
Frontier Airlines: 80% of its 557 flights on the route arrived on time. Southwest Airlines: 69%. United Airlines: 79%.
What month has the most delays from DEN to ONT?
June (60% on time). The best month is December (81%), over 2023–2026.
Is the last flight of the day from DEN to ONT more likely to be cancelled?
Yes. Each airline's last DEN–ONT flight of the day was cancelled 0.4% of the time over the past year, against 0.1% for its earlier flights. If the last flight is cancelled, the next one is usually the following morning.
Related
- ONT → DEN (return)
- Denver (DEN) delays by hour
- Flights into Ontario (ONT)
- Southwest Airlines on-time record
- United Airlines on-time record
- Frontier Airlines on-time record
- Connecting off this flight? Check the risk
Domestic flights by the airlines that report to the U.S. DOT, plus their regional partners. "On time" means arriving less than 15 minutes after schedule; cancelled and diverted flights count as not on time. Past performance is a guide, not a forecast. Method.