About 1 in 4 F9 1261 flights from Denver arrived 15+ minutes late, diverted or cancelled over the past year (24%); 0.7% were cancelled. The typical flight landed 8 minutes early.
F9 1261: DEN → ONT
Scheduled to leave Denver at 10:29 p.m. local time. Over the past year it arrived on time 76% of the time (270 flights), better than other F9 flights on the route at that hour (70%). Last seen in the data Aug 31, 2026.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 42 | 64% |
| Tuesday | 35 | 77% |
| Wednesday | 35 | 74% |
| Thursday | 40 | 78% |
| Friday | 39 | 79% |
| Saturday | 38 | 76% |
| Sunday | 41 | 85% |
Why it was late
All flights DEN → ONT · Connecting off F9 1261? Check the risk
Questions
How often is F9 1261 from DEN to ONT late?
Frontier Airlines 1261 from Denver, CO to Ontario, CA arrived 15 or more minutes late, was diverted or was cancelled on 24% of 270 scheduled flights between September 2025 and August 2026. 0.7% were cancelled.
Flight numbers change. Figures cover flights with this airline, number and route only. "Likely range" is the 95% interval for the true on-time rate given the number of flights. This is history, not live status: check Frontier Airlines for today's flight. Method.