Route profile
DEN→ONT
Flight reliability, delays and best times to fly from Denver to Ontario, 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 46% of comparable major US routes (4,598 compared)
Calculated from 8,691 flights. How this is calculated
DEN → ONT arrives on time 74.4% of the time; the return trip, ONT → DEN, arrives on time 82.3% of the time, a 7.8-point gap between the two directions of the same city pair.
DEN → ONT spends 22.0 minutes on the ground on an 819-mile trip: 16.9 minutes from pushback to wheels-up at DEN and 5.1 minutes from touchdown to gate at ONT.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
This route has stayed remarkably steady year over year, a smaller swing than 97% of 5,368 comparable routes.
74.9% on time over the most recent 12 months (2025-08 to 2026-07), against 75.1% in the 12 months before (2024-08 to 2025-07), virtually unchanged.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 5,368 in the comparison.
What sets this route apart
Where DEN to ONT differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
DEN to ONT struggles most at 6 PM: 57.0% of its flights scheduled then arrive on time, 10.6 points behind the 67.6% on routes of similar length at the same hour. Against all other routes the gap is 11.6 points.
Monday is the day DEN to ONT slips furthest against routes of similar length, 71.2% on time where they average 77.0%, 5.8 points lower. Against all other routes the gap is 6.1 points.
In June, DEN to ONT runs 10.9 points below routes of similar length, 60.9% on time to 71.8%. Against all other routes the gap is 11.8 points.
Southwest Airlines’ flights on DEN to ONT arrive on time 70.9% of the time, 6.3 points below the 77.2% it manages on its routes of similar length. Against all other routes the gap is 6.5 points.
Frontier Airlines does better on DEN to ONT than on its routes of similar length: 77.7% on time here, 72.0% there, 5.7 points apart. Against all other routes the gap is 6.5 points.
DEN to ONT against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 6 PM departures | 57.0% | routes of similar length | 67.6% | −10.6 pts | 456 here, 151,414 there |
| Weekday: Monday | 71.2% | routes of similar length | 77.0% | −5.8 pts | 1,304 here, 339,183 there |
| Month: June | 60.9% | routes of similar length | 71.8% | −10.9 pts | 769 here, 189,197 there |
| Airline: Southwest Airlines | 70.9% | routes of similar length | 77.2% | −6.3 pts | 4,086 here, 631,496 there |
| Airline: Frontier Airlines | 77.7% | routes of similar length | 72.0% | +5.7 pts | 1,957 here, 113,910 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 DEN → ONT flights are cancelled
July 2023 – July 2026
DEN → ONT cancelled 52 of 8,691 scheduled flights — about 1 in every 167. The reason filed most often was extreme weather, 48.1% of the cancellations coded on this route — about 1 in every 348 scheduled flights.
Share of cancellations
Of 52 cancelled departures carrying a reason code.
What each reason means
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
25 cancellations, 48.1% of the total.
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
20 cancellations, 38.5% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
7 cancellations, 13.5% 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.
52 coded cancellations were recorded on DEN → ONT; the section appears from 50.
When it goes wrong
July 2023 – July 2026
49 min late
against a median of 3 min early
Percentiles over 8,691 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at ONT after arriving from DEN.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 43% | Likely to miss |
| 45 min | 25% | High risk |
| 60 min | 16% | High risk |
| 90 min | 7.8% | Some risk |
| 120 min | 4.1% | 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 0.60% of the time and diverts 0.07% of the time, which a late arrival never shows up in.
Chance of missing is the share of 8,633 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 49 minutes late (90th-percentile gate arrival delay), over 8,691 operations.
Any other layover length: connection checker.
Best time to fly
DEN → ONT flights departing 5–9 AM arrived on time 88.3% of the time, against 64.8% for 9 PM–5 AM departures, a gap of 23.5 percentage points.
By departure window
By departure hour
- 12 AM to 5 AM: too few flights to score
- 6 AM: 89.2% on time from 159 flights
- 7 AM: 85.4% on time from 413 flights
- 8 AM: 89.6% on time from 756 flights
- 9 AM: 84.6% on time from 281 flights
- 10 AM: 87.4% on time from 215 flights
- 11 AM: 83.6% on time from 1,288 flights
- 12 PM: 75.2% on time from 243 flights
- 1 PM: 77.9% on time from 397 flights
- 2 PM: 73.2% on time from 277 flights
- 3 PM: too few flights to score
- 4 PM: 71.6% on time from 425 flights
- 5 PM: 68.2% on time from 170 flights
- 6 PM: 57.0% on time from 457 flights
- 7 PM: 67.8% on time from 1,377 flights
- 8 PM: 67.6% on time from 329 flights
- 9 PM: 61.5% on time from 523 flights
- 10 PM: 66.3% on time from 1,125 flights
- 11 PM: too few flights to score
Why DEN → ONT runs late
July 2023 – July 2026
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
airspace and airport capacity, including weather-driven flow 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 DEN → ONT. Only delays of 15 minutes or more are attributed.
Late-arriving aircraft is the largest cause on DEN → ONT, at 54.7%: flights here mostly leave late because the plane came in late, and the day shows it: 5–9 AM departures arrived on time 88.3% of the time and 9 PM–5 AM departures 64.8%.
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 | 4,117 | 70.9% | 0.68% | 1 min | 7.9% |
| United Airlines | 2,595 | 77.6% | 0.31% | -5 min | 8.5% |
| Frontier Airlines | 1,973 | 77.7% | 0.81% | -7 min | 7.8% |
Southwest Airlines flew 47.4% of the 8,685 flights listed.
Frontier Airlines arrived on time 6.8 percentage points more often than Southwest Airlines on this route.
Other ways to fly Denver to Los Angeles
Airport pairs in the same two city markets, as the DOT defines them.
DEN → SNA is the most reliable pairing for this journey at 79.9% on time, against 74.4% for DEN → ONT.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
Weekly and seasonal patterns
By day of week
Wednesday is historically the most reliable day and Monday the least, a gap of 7.1 percentage points.
By month
- Jan: 77.4%
- Feb: 76.2%
- Mar: 80.6%
- Apr: 79.7%
- May: 73.7%
- Jun: 60.9%
- Jul: 65.2%
- Aug: 69.1%
- Sep: 76.5%
- Oct: 79.3%
- Nov: 81.2%
- Dec: 81.1%
June is historically the weakest month and November the strongest, a spread of 20.3 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 57.2% from 251 flights
- August 2023: 65.1% from 262 flights
- September 2023: 72.2% from 235 flights
- October 2023: 74.1% from 244 flights
- November 2023: 85.1% from 235 flights
- December 2023: 86.5% from 245 flights
- January 2024: 73.9% from 229 flights
- February 2024: 72.0% from 219 flights
- March 2024: 76.8% from 237 flights
- April 2024: 81.9% from 232 flights
- May 2024: 72.5% from 247 flights
- June 2024: 66.9% from 264 flights
- July 2024: 72.1% from 273 flights
- August 2024: 71.4% from 263 flights
- September 2024: 81.1% from 249 flights
- October 2024: 89.2% from 259 flights
- November 2024: 74.8% from 224 flights
- December 2024: 85.7% from 223 flights
- January 2025: 76.5% from 209 flights
- February 2025: 75.4% from 187 flights
- March 2025: 82.5% from 217 flights
- April 2025: 76.2% from 252 flights
- May 2025: 74.2% from 260 flights
- June 2025: 59.5% from 261 flights
- July 2025: 58.5% from 272 flights
- August 2025: 70.9% from 254 flights
- September 2025: 75.8% from 236 flights
- October 2025: 73.9% from 242 flights
- November 2025: 83.6% from 220 flights
- December 2025: 69.1% from 194 flights
- January 2026: 82.7% from 185 flights
- February 2026: 82.5% from 171 flights
- March 2026: 83.0% from 200 flights
- April 2026: 81.5% from 205 flights
- May 2026: 74.4% from 242 flights
- June 2026: 55.8% from 250 flights
- July 2026: 72.8% from 243 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 74.9% against 75.1% in the 12 months before — broadly unchanged.
Data and methodology
Calculated by FlyerIntel from 8,691 DEN → ONT 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