Route on-time record
DEN to ONT: most on-time flights and the best time to fly
Denver (Denver International Airport) to Ontario (Ontario International Airport). 2,682 nonstop flights in Jun 2025 to May 2026, 74% arrived within 15 minutes and 0.3% were cancelled. The most reliable flight number was Southwest 4040 at 8:30 AM.
Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.
DEN → ONT
Denver to Ontario: 2,682 nonstop flights a year
On time (12 months)
74%
Cancelled
0.3%
avg delay 16 min
Best time to leave
Before 9 AM
89% on time vs 62% after 9 PM
Most reliable airline
Frontier
78% chance on time
Lowest nonstop fare seen in the next two months: $240 (Frontier 2907 on 2026-10-25). Fares open on our travel partner (Aviasales). Pick the flight number you chose here.
Most reliable nonstop flights
Ranked by the chance the flight operates and arrives within 15 minutes of schedule, from Jun 2025 to May 2026 records.
#1 · Southwest 4040
8:30 AM → 9:50 AM2h 20m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Southwest 106, 3787; its record covers all of them.
90%
chance on time
- On time (history)
- 94%
- Cancelled
- 0.0%
- Avg arrival delay
- 3 min
- Arrived on time 94% of the time (88 flights, Jun 2025 to May 2026).
- Never cancelled in 88 scheduled flights.
- Leaves in this route's most on-time window (Before 9 AM: 89% on time; After 9 PM: 62%).
- Departs outside DEN's trouble window (2 PM to 8 PM, when 79% of its 174 ground stops and delay programs started).
Moderate track record · 88 flights
Find Southwest 4040 fares Opens this date on Aviasales#2 · Frontier 2907
8:41 AM → 10:05 AM2h 24m nonstop
Local times, typical schedule. Last flown 2026-05-31.
89%
chance on time
- On time (history)
- 90%
- Cancelled
- 0.0%
- Avg arrival delay
- 5 min
- Arrived on time 90% of the time (48 flights, Jun 2025 to May 2026).
- Never cancelled in 48 scheduled flights.
- Leaves in this route's most on-time window (Before 9 AM: 89% on time; After 9 PM: 62%).
- Departs outside DEN's trouble window (2 PM to 8 PM, when 79% of its 174 ground stops and delay programs started).
Limited track record · 48 flights
Find Frontier 2907 fares Opens this date on Aviasales#3 · United 430
11:15 AM → 12:38 PM2h 23m nonstop
Local times, typical schedule. Last flown 2026-05-31.
87%
chance on time
- On time (history)
- 87%
- Cancelled
- 0.3%
- Avg arrival delay
- 9 min
- Arrived on time 87% of the time (363 flights, Jun 2025 to May 2026).
- Departs outside DEN's trouble window (2 PM to 8 PM, when 79% of its 174 ground stops and delay programs started).
Strong track record · 363 flights
Find United 430 fares Opens this date on Aviasales#4 · Frontier 1261
10:29 PM → 11:49 PM2h 26m nonstop
Local times, typical schedule. Last flown 2026-05-31.
84%
chance on time
- On time (history)
- 86%
- Cancelled
- 0.0%
- Avg arrival delay
- 11 min
- Arrived on time 86% of the time (264 flights, Jun 2025 to May 2026).
- Never cancelled in 264 scheduled flights.
- Leaves in this route's least on-time window (After 9 PM: 62% on time; Before 9 AM: 89%).
- Departs outside DEN's trouble window (2 PM to 8 PM, when 79% of its 174 ground stops and delay programs started).
Strong track record · 264 flights
Find Frontier 1261 fares Opens this date on Aviasales#5 · United 450
7:10 PM → 8:36 PM2h 26m nonstop
Local times, typical schedule. Last flown 2026-04-29.
81%
chance on time
- On time (history)
- 94%
- Cancelled
- 0.0%
- Avg arrival delay
- 8 min
- Arrived on time 94% of the time (32 flights, Jun 2025 to May 2026).
- Never cancelled in 32 scheduled flights.
- Departs inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
- Short track record (32 flights), so its score leans on the airline's record at this hour.
Limited track record · 32 flights
Find United 450 fares Opens this date on Aviasales#6 · United 2028
7:20 PM → 8:36 PM2h 26m nonstop
Local times, typical schedule. Last flown 2026-05-31.
76%
chance on time
- On time (history)
- 81%
- Cancelled
- 0.0%
- Avg arrival delay
- 12 min
- Arrived on time 81% of the time (109 flights, Jun 2025 to May 2026).
- Never cancelled in 109 scheduled flights.
- Departs inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
Moderate track record · 109 flights
Find United 2028 fares Opens this date on Aviasales#7 · Southwest 3662
3:25 PM → 4:45 PM2h 20m nonstop
Local times, typical schedule. Last flown 2026-05-30.
76%
chance on time
- On time (history)
- 100%
- Cancelled
- 0.0%
- Avg arrival delay
- 0 min
- Arrived on time 100% of the time (8 flights, Jun 2025 to May 2026).
- Departs inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
- Short track record (8 flights), so its score leans on the airline's record at this hour.
Limited track record · 8 flights
Find Southwest 3662 fares Opens this date on Aviasales#8 · Southwest 1353
1:45 PM → 3:10 PM2h 25m nonstop
Local times, typical schedule. Last flown 2026-05-31.
75%
chance on time
- On time (history)
- 83%
- Cancelled
- 0.0%
- Avg arrival delay
- 8 min
- Arrived on time 83% of the time (23 flights, Jun 2025 to May 2026).
- Departs outside DEN's trouble window (2 PM to 8 PM, when 79% of its 174 ground stops and delay programs started).
- Short track record (23 flights), so its score leans on the airline's record at this hour.
Limited track record · 23 flights
Find Southwest 1353 fares Opens this date on Aviasales#9 · United 1656
4:05 PM → 5:28 PM2h 23m nonstop
Local times, typical schedule. Last flown 2026-05-31.
74%
chance on time
- On time (history)
- 67%
- Cancelled
- 0.0%
- Avg arrival delay
- 55 min
- Arrived on time 67% of the time (9 flights, Jun 2025 to May 2026).
- Departs inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
- 61% of its delay minutes came from the plane arriving late from an earlier flight.
- Short track record (9 flights), so its score leans on the airline's record at this hour.
Limited track record · 9 flights
Find United 1656 fares Opens this date on Aviasales#10 · Southwest 2877
11:50 AM → 1:10 PM2h 20m nonstop
Local times, typical schedule. Last flown 2026-05-29.
73%
chance on time
- On time (history)
- 65%
- Cancelled
- 0.0%
- Avg arrival delay
- 10 min
- Arrived on time 65% of the time (23 flights, Jun 2025 to May 2026).
- Departs outside DEN's trouble window (2 PM to 8 PM, when 79% of its 174 ground stops and delay programs started).
- Short track record (23 flights), so its score leans on the airline's record at this hour.
Limited track record · 23 flights
Find Southwest 2877 fares Opens this date on Aviasales
Airlines on this route
Season-adjusted chance of operating and arriving on time.
- Frontier Airlines78%
546 flights · 79% on time as flown · 0.4% cancel
- United Airlines77%
867 flights · 77% on time as flown · 0.2% cancel
- Southwest Airlines69%
1,269 flights · 69% on time as flown · 0.3% cancel
On time by departure time
All airlines, scheduled local departure, Jun 2025 to May 2026.
- Before 9 AM89%
501 flights · avg delay 5 min
- 9 AM to noon86%
467 flights · avg delay 9 min
- Noon to 3 PM75%
272 flights · avg delay 12 min
- 3 to 6 PM70%
203 flights · avg delay 23 min
- 6 to 9 PM64%
727 flights · avg delay 24 min
- After 9 PM62%
512 flights · avg delay 24 min
Best day: Wednesday (79%). Worst: Monday (71%).
Smarter routing
Nearby airports that run more on time
DEN → SNA 80% chance on time
Denver International Airport to John Wayne Orange County International Airport · 3,708 flights a year · 30 mi from your airports · yours: 74%
DEN → LAX 79% chance on time
Denver International Airport to Los Angeles International Airport · 7,728 flights a year · 47 mi from your airports · yours: 74%
On time by month
All airlines, Jun 2023 to May 2026. Several years per month, so one stormy season doesn't define a month. Travel-month estimates use this seasonal pattern.
What delays this route
- Late-arriving aircraft57%
- Airline (crew, maintenance, boarding)34%
- Air traffic control and airport volume8%
Share of delay minutes by the cause airlines report to the US DOT.
Historical odds, not a guarantee. Built from the US DOT Bureau of Transportation Statistics on-time reports (Jun 2025 to May 2026), FAA ground stop and delay program advisories, and 20 years of airport weather observations. Covers US airlines that report to the DOT; schedules are flights operated recently, so confirm times when you book. ATIS Alerts is not affiliated with any airline. Fares are what Aviasales travelers saw in recent searches (USD, one way, 1 adult), not live quotes; the partner site shows the current price. Fare links go to our travel partner and may earn us a commission at no cost to you. Affiliate disclosure
DEN to ONT questions
- What time of day is best to fly DEN to ONT?
- Before 9 AM: 89% of flights arrived on time, against 62% for departures after 9 PM. Later flights inherit delays from earlier ones, so the first departures of the day usually run best.
- Which airline is most on time from DEN to ONT?
- Frontier, with a season-adjusted 78% chance of operating and arriving on time over 546 flights. The adjustment compares each airline with what the route did in the months it flew, so a carrier that skipped a stormy month gets no free credit.
- What is the worst month for delays on DEN to ONT?
- June (61% on time); the best was November (81%), averaged over Jun 2023 to May 2026.
- Is this a prediction for my flight?
- No. These are historical odds from the US DOT on-time reports, FAA advisories and airport weather records. Check your flight status and the FAA delay board on the day you fly.
More routes from DEN
- ONT to DEN (return)
- DEN to PHX 75%
- DEN to SLC 77%
- DEN to LAX 79%
- DEN to LAS 75%
- DEN to SEA 73%
- DEN to ORD 70%
- DEN to DFW 75%
- DEN to SAN 76%
- DEN to MSP 78%
- DEN to ATL 80%
- DEN to SFO 68%
- DEN to AUS 76%
Live status: FAA delays and ground stops