DEN to ONT flight delays & on-time performance
Nonstop flights from Denver International Airport to Ontario International Airport · 819 miles · Aug 2025 – Jul 2026
No FAA-reported ground stops or delays at DEN or ONT right now. Individual flights can still be delayed by the airline; check with your airline for your flight.
Key facts
- Flights from Denver (DEN) to Ontario (ONT) arrived on time 75% of the time in Aug 2025 – Jul 2026, worse than the 78% national average.
- 0.1% were cancelled, and 8% arrived an hour or more late.
- Frontier Airlines was the most punctual airline here (80% on time); Southwest Airlines was the least (70%).
- Departures scheduled around 8am did best (91% on time); around 9pm did worst (54%).
- Wednesday was the most reliable day to fly (81% on time) and Monday the least (68%).
- The largest source of delay minutes was late-arriving aircraft (55%).
Which airline is most on time from DEN to ONT?
Ranked by on-time arrival rate. Regional airlines fly under their partner's brand (e.g. SkyWest for Delta Connection or United Express).
| Airline | On time | Cancelled | Avg delay | 1 hr+ late | Flights |
|---|---|---|---|---|---|
| Frontier Airlines | 80% | 0.2% | 13 min | 6.9% | 551 |
| United Airlines | 80% | 0.0% | 15 min | 8.8% | 823 |
| Southwest Airlines | 70% | 0.1% | 16 min | 7.9% | 1,268 |
Best time of day to fly
On-time arrival rate by scheduled departure hour (local time).
- 6am97%35 flights
- 7am86%128 flights
- 8am91%349 flights
- 9am88%32 flights
- 10am77%43 flights
- 11am86%416 flights
- 1pm78%176 flights
- 2pm78%41 flights
- 4pm73%122 flights
- 5pm50%44 flights
- 6pm54%177 flights
- 7pm72%396 flights
- 8pm64%154 flights
- 9pm54%147 flights
- 10pm67%350 flights
Best day of the week
On-time arrival rate by day of departure.
- Monday68%0.0% cancelled
- Tuesday78%0.3% cancelled
- Wednesday81%0.0% cancelled
- Thursday72%0.2% cancelled
- Friday75%0.0% cancelled
- Saturday78%0.0% cancelled
- Sunday74%0.0% cancelled
On-time trend by month
Why flights are late
Share of delay minutes by cause, as reported by airlines to the DOT.
- Late-arriving aircraft55%
- Airline (crew, maintenance, cleaning, fueling)35%
- Air traffic control & airport congestion9%
- Extreme weather1%
- Security0%
Why flights are cancelled
Share of cancellations by reason.
- Airline (crew, maintenance, cleaning, fueling)50%
- Air traffic control & airport congestion50%
- Extreme weather0%
- Security0%
DEN to ONT: common questions
- How often are DEN to ONT flights on time?
- 75% of flights arrived less than 15 minutes late in Aug 2025 – Jul 2026, compared with 78% for all US flights.
- How often are flights from Denver to Ontario cancelled?
- 0.1% of scheduled flights were cancelled (2 of 2,642).
- How long are typical delays?
- Across all flights the average arrival delay was 15 min (early arrivals count as zero). Flights that were late arrived 56 min behind schedule on average, and 8.0% of flights were an hour or more late.
- How long is taxi time at DEN?
- Flights on this route spent 18 min taxiing from the gate to takeoff on average.
Related routes
Return trip: ONT to DEN — 81% on time
More flights from Denver
Data: U.S. DOT Bureau of Transportation Statistics, Aug 2025 – Jul 2026 (12 months). Latest month published by BTS: July 2026. Route: DEN → ONT, nonstop flights by US airlines that report to the DOT. How we calculate this.