About 1 in 5 UA 1263 flights from Ontario arrived 15+ minutes late, diverted or cancelled over the past year (20%); 0.4% were cancelled. The typical flight landed 7 minutes early.
UA 1263: ONT → DEN
Scheduled to leave Ontario at 1:18 p.m. local time. Over the past year it arrived on time 80% of the time (237 flights), in line with other UA flights on the route at that hour (81%). Last seen in the data Aug 31, 2026.
Usually United Airlines's last flight of the day from Ontario to Denver (89% of days). United Airlines's last ONT–DEN flight was cancelled 0.5% of the time, against 0.2% for its earlier ones. If it's cancelled, the next United Airlines flight is usually around 5:00 a.m. the next morning.
Month by month
By day of week
| Day | Flights | On time |
|---|---|---|
| Monday | 34 | 85% |
| Tuesday | 34 | 76% |
| Wednesday | 34 | 74% |
| Thursday | 34 | 76% |
| Friday | 34 | 79% |
| Saturday | 33 | 73% |
| Sunday | 34 | 94% |
Why it was late
All flights ONT → DEN · Connecting off UA 1263? Check the risk
Questions
How often is UA 1263 from ONT to DEN late?
United Airlines 1263 from Ontario, CA to Denver, CO arrived 15 or more minutes late, was diverted or was cancelled on 20% of 237 scheduled flights between September 2025 and August 2026. 0.4% 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 United Airlines for today's flight. Method.