Route profile
ONT→DEN
Flight reliability, delays and best times to fly from Ontario to Denver, 819 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 72% of comparable major US routes (4,598 compared)
Calculated from 8,674 flights. How this is calculated
ONT → DEN arrives on time 82.3% of the time; the return trip, DEN → ONT, arrives on time 74.4% of the time, a 7.8-point gap between the two directions of the same city pair.
ONT → DEN spends 22.4 minutes on the ground on an 819-mile trip: 13.1 minutes from pushback to wheels-up at ONT and 9.3 minutes from touchdown to gate at DEN.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What sets this route apart
Where ONT to DEN differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
ONT to DEN is at its best against routes of similar length for flights scheduled at 8 PM: 82.4% arrive on time, 15.7 points ahead of the 66.7% those routes manage at that hour. Against all other routes the gap is 15 points.
ONT to DEN struggles most at 2 PM: 64.4% of its flights scheduled then arrive on time, 10 points behind the 74.4% on routes of similar length at the same hour. Against all other routes the gap is 10.2 points.
ONT to DEN holds up on Sundays better than routes of similar length do: 82.2% on time to their 74.4%, a 7.8 points lead. Against all other routes the gap is 7.4 points.
December is kinder to ONT to DEN than to routes of similar length: 87.0% on time against 78.8%, 8.2 points better. Against all other routes the gap is 8.3 points.
Frontier Airlines does better on ONT to DEN than on its routes of similar length: 79.7% on time here, 72.0% there, 7.7 points apart. Against all other routes the gap is 8.5 points.
ONT to DEN against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 8 PM departures | 82.4% | routes of similar length | 66.7% | +15.7 pts | 125 here, 117,631 there |
| Hour: 2 PM departures | 64.4% | routes of similar length | 74.4% | −10.0 pts | 354 here, 134,518 there |
| Weekday: Sunday | 82.2% | routes of similar length | 74.4% | +7.8 pts | 1,240 here, 335,740 there |
| Month: December | 87.0% | routes of similar length | 78.8% | +8.2 pts | 662 here, 186,711 there |
| Airline: Frontier Airlines | 79.7% | routes of similar length | 72.0% | +7.7 pts | 1,949 here, 113,918 there |
Each comparison pools the flights of other routes, with this route’s own left out. Similar length means within 15% of this route’s 819 miles, with at least 5 such routes. A bucket is set against the most comparable group that has enough flights: similar length, then the same origin (at least 3 routes), then all other routes. Hours, weekdays and months appear only where both sides have 120 completed flights, and airlines where both have 600. The gap must be at least 2 points and 2 standard errors, and only the largest gap each way is kept per measure. These are differences in the flights counted, not causes.
Why ONT → DEN flights are cancelled
July 2023 – July 2026
ONT → DEN cancelled 63 of 8,674 scheduled flights — about 1 in every 138. The reason filed most often was the airline, 49.2% of the cancellations coded on this route — about 1 in every 280 scheduled flights.
Share of cancellations
Of 63 cancelled departures carrying a reason code.
What each reason means
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
31 cancellations, 49.2% of the total.
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
28 cancellations, 44.4% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
4 cancellations, 6.3% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
63 coded cancellations were recorded on ONT → DEN; the section appears from 50.
When it goes wrong
July 2023 – July 2026
35 min late
against a median of 8 min early
Percentiles over 8,674 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at DEN after arriving from ONT.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 32% | Likely to miss |
| 45 min | 17% | High risk |
| 60 min | 11% | Some risk |
| 90 min | 6.5% | Some risk |
| 120 min | 4.0% | Low risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 0.73% of the time and diverts 0.32% of the time, which a late arrival never shows up in.
Chance of missing is the share of 8,583 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 35 minutes late (90th-percentile gate arrival delay), over 8,674 operations.
Any other layover length: connection checker.
Best time to fly
ONT → DEN flights departing 5–9 AM arrived on time 93.0% of the time, against 64.3% for 3–6 PM departures, a gap of 28.7 percentage points.
By departure window
By departure hour
- 12 AM: 79.6% on time from 417 flights
- 1 AM to 4 AM: too few flights to score
- 5 AM: 94.9% on time from 2,197 flights
- 6 AM: 88.3% on time from 553 flights
- 7 AM: 86.1% on time from 248 flights
- 8 AM: 92.8% on time from 548 flights
- 9 AM: 92.1% on time from 219 flights
- 10 AM: 82.8% on time from 276 flights
- 11 AM: 83.5% on time from 221 flights
- 12 PM: 78.1% on time from 323 flights
- 1 PM: 76.3% on time from 1,541 flights
- 2 PM: 64.4% on time from 361 flights
- 3 PM: 65.3% on time from 413 flights
- 4 PM: 63.6% on time from 361 flights
- 5 PM: 63.8% on time from 273 flights
- 6 PM: 77.7% on time from 448 flights
- 7 PM: too few flights to score
- 8 PM: 82.4% on time from 125 flights
- 9 PM to 11 PM: too few flights to score
Why ONT → DEN runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
airspace and airport capacity, including weather-driven flow control
crew, maintenance, boarding and fueling, all within the carrier’s control
weather severe enough to stop this flight specifically
screening or terminal security incidents
Share of the delay minutes US DOT attributed to each cause for ONT → DEN. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on ONT → DEN, at 41.3%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 93.0% of the time and 3–6 PM departures 64.3%.
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| Southwest Airlines | 4,101 | 81.8% | 0.63% | -5 min | 6.1% |
| United Airlines | 2,594 | 85.0% | 0.58% | -12 min | 6.2% |
| Frontier Airlines | 1,972 | 79.7% | 1.12% | -8 min | 8.2% |
Southwest Airlines flew 47.3% of the 8,667 flights listed.
United Airlines arrived on time 5.3 percentage points more often than Frontier Airlines on this route.
Other ways to fly Los Angeles to Denver
Airport pairs in the same two city markets, as the DOT defines them.
Flying to DEN from the Los Angeles area? Compare ONT, LAX, SNA, BUR for DEN, with the same test for what counts as a real difference.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
| Flight | Scheduled | Operations | On time |
|---|---|---|---|
| F91500 Frontier Airlines | 12:59 AM | 828 | 85.3% |
Weekly and seasonal patterns
By day of week
Saturday is historically the most reliable day and Monday the least, a gap of 5.7 percentage points.
By month
- Jan: 85.5%
- Feb: 85.2%
- Mar: 81.9%
- Apr: 83.3%
- May: 78.7%
- Jun: 74.9%
- Jul: 74.7%
- Aug: 80.2%
- Sep: 86.8%
- Oct: 87.6%
- Nov: 87.0%
- Dec: 87.0%
July is historically the weakest month and October the strongest, a spread of 12.9 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 72.8% from 251 flights
- August 2023: 84.0% from 264 flights
- September 2023: 88.8% from 237 flights
- October 2023: 86.0% from 244 flights
- November 2023: 89.8% from 235 flights
- December 2023: 92.7% from 245 flights
- January 2024: 88.4% from 229 flights
- February 2024: 81.6% from 219 flights
- March 2024: 86.1% from 226 flights
- April 2024: 87.2% from 228 flights
- May 2024: 84.1% from 247 flights
- June 2024: 81.2% from 262 flights
- July 2024: 82.7% from 273 flights
- August 2024: 82.9% from 263 flights
- September 2024: 90.4% from 249 flights
- October 2024: 90.3% from 259 flights
- November 2024: 87.4% from 224 flights
- December 2024: 89.2% from 223 flights
- January 2025: 80.1% from 208 flights
- February 2025: 88.2% from 187 flights
- March 2025: 85.8% from 213 flights
- April 2025: 77.2% from 252 flights
- May 2025: 68.5% from 261 flights
- June 2025: 66.1% from 260 flights
- July 2025: 65.2% from 272 flights
- August 2025: 73.7% from 254 flights
- September 2025: 81.0% from 237 flights
- October 2025: 86.2% from 241 flights
- November 2025: 83.6% from 220 flights
- December 2025: 77.3% from 195 flights
- January 2026: 88.0% from 185 flights
- February 2026: 86.4% from 171 flights
- March 2026: 73.0% from 200 flights
- April 2026: 86.3% from 205 flights
- May 2026: 83.9% from 242 flights
- June 2026: 77.4% from 250 flights
- July 2026: 78.2% from 243 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 81.0% against 80.4% in the 12 months before — broadly unchanged.
Data and methodology
Calculated by FlyerIntel from 8,674 ONT → DEN flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed