Route on-time record
ONT to DEN: most on-time flights and the best time to fly
Ontario (Ontario International Airport) to Denver (Denver International Airport). 2,682 nonstop flights in Jun 2025 to May 2026, 79% arrived within 15 minutes and 0.6% were cancelled. The most reliable flight number was United 2446 at 5:00 AM.
Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.
ONT → DEN
Ontario to Denver: 2,682 nonstop flights a year
On time (12 months)
79%
Cancelled
0.6%
avg delay 16 min
Best time to leave
Before 9 AM
91% on time vs 49% 3 to 6 PM
Most reliable airline
United
83% chance on time
Lowest nonstop fare seen in the next two months: $32 (Frontier 1500 on 2026-11-12). 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 · United 2446
5:00 AM → 8:32 AM2h 22m nonstop
Local times, typical schedule. Last flown 2026-05-31.
91%
chance on time
- On time (history)
- 93%
- Cancelled
- 0.5%
- Avg arrival delay
- 4 min
- Arrived on time 93% of the time (209 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 91% on time; 3 to 6 PM: 49%).
Strong track record · 209 flights
Find United 2446 fares Opens this date on Aviasales#2 · Southwest 1666
6:25 AM → 9:35 AM2h 10m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Southwest 4129; its record covers all of them.
87%
chance on time
- On time (history)
- 91%
- Cancelled
- 0.0%
- Avg arrival delay
- 4 min
- Arrived on time 91% 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: 91% on time; 3 to 6 PM: 49%).
Moderate track record · 88 flights
Find Southwest 1666 fares Opens this date on Aviasales#3 · Southwest 113
8:00 AM → 11:10 AM2h 10m nonstop
Local times, typical schedule. Last flown 2026-05-31.
86%
chance on time
- On time (history)
- 89%
- Cancelled
- 0.0%
- Avg arrival delay
- 5 min
- Arrived on time 89% of the time (55 flights, Jun 2025 to May 2026).
- Never cancelled in 55 scheduled flights.
- Leaves in this route's most on-time window (Before 9 AM: 91% on time; 3 to 6 PM: 49%).
- Short track record (55 flights), so its score leans on the airline's record at this hour.
Limited track record · 55 flights
Find Southwest 113 fares Opens this date on Aviasales#4 · United 1263
1:34 PM → 4:56 PM2h 22m nonstop
Local times, typical schedule. Last flown 2026-05-31.
84%
chance on time
- On time (history)
- 88%
- Cancelled
- 0.7%
- Avg arrival delay
- 13 min
- Arrived on time 88% of the time (145 flights, Jun 2025 to May 2026).
- Lands inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
- 62% of its delay minutes came from the plane arriving late from an earlier flight.
Moderate track record · 145 flights
Find United 1263 fares Opens this date on Aviasales#5 · Southwest 4132
8:25 AM → 11:40 AM2h 15m nonstop
Local times, typical schedule. Last flown 2026-04-06.
84%
chance on time
- On time (history)
- 80%
- Cancelled
- 0.0%
- Avg arrival delay
- 14 min
- Arrived on time 80% of the time (15 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 91% on time; 3 to 6 PM: 49%).
- Short track record (15 flights), so its score leans on the airline's record at this hour.
Limited track record · 15 flights
Find Southwest 4132 fares Opens this date on Aviasales#6 · Frontier 1500
6:00 AM → 9:22 AM2h 20m nonstop
Local times, typical schedule. Last flown 2026-05-31.
83%
chance on time
- On time (history)
- 84%
- Cancelled
- 0.6%
- Avg arrival delay
- 13 min
- Arrived on time 84% of the time (312 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 91% on time; 3 to 6 PM: 49%).
- 50% of its delay minutes came from the plane arriving late from an earlier flight.
Strong track record · 312 flights
Find Frontier 1500 fares Opens this date on Aviasales#7 · United 1316
6:30 PM → 9:51 PM2h 21m nonstop
Local times, typical schedule. Last flown 2026-05-31.
76%
chance on time
- On time (history)
- 67%
- Cancelled
- 0.0%
- Avg arrival delay
- 42 min
- Arrived on time 67% of the time (9 flights, Jun 2025 to May 2026).
- 100% 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 1316 fares Opens this date on Aviasales#8 · Southwest 542
1:40 PM → 4:55 PM2h 15m nonstop
Local times, typical schedule. Last flown 2026-04-01.
74%
chance on time
- On time (history)
- 75%
- Cancelled
- 0.0%
- Avg arrival delay
- 11 min
- Arrived on time 75% of the time (8 flights, Jun 2025 to May 2026).
- Lands inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
- 92% of its delay minutes came from the plane arriving late from an earlier flight.
- Short track record (8 flights), so its score leans on the airline's record at this hour.
Limited track record · 8 flights
Find Southwest 542 fares Opens this date on Aviasales#9 · Frontier 2908
10:50 AM → 2:12 PM2h 22m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Frontier 1262; its record covers all of them.
68%
chance on time
- On time (history)
- 66%
- Cancelled
- 1.3%
- Avg arrival delay
- 31 min
- Arrived on time 66% of the time (229 flights, Jun 2025 to May 2026).
- Lands inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
Strong track record · 229 flights
Find Frontier 2908 fares Opens this date on Aviasales#10 · Southwest 4671
1:10 PM → 4:20 PM2h 10m nonstop
Local times, typical schedule. Last flown 2026-04-06.
66%
chance on time
- On time (history)
- 50%
- Cancelled
- 0.0%
- Avg arrival delay
- 21 min
- Arrived on time 50% of the time (20 flights, Jun 2025 to May 2026).
- Lands inside DEN's trouble window: 79% of its 174 ground stops and delay programs started between 2 PM and 8 PM.
- Short track record (20 flights), so its score leans on the airline's record at this hour.
Limited track record · 20 flights
Find Southwest 4671 fares Opens this date on Aviasales
Airlines on this route
Season-adjusted chance of operating and arriving on time.
- United Airlines83%
867 flights · 83% on time as flown · 0.6% cancel
- Frontier Airlines76%
546 flights · 77% on time as flown · 0.8% cancel
- Southwest Airlines76%
1,269 flights · 76% on time as flown · 0.4% cancel
On time by departure time
All airlines, scheduled local departure, Jun 2025 to May 2026.
- Before 9 AM91%
1,083 flights · avg delay 6 min
- 9 AM to noon83%
265 flights · avg delay 11 min
- Noon to 3 PM72%
692 flights · avg delay 20 min
- 3 to 6 PM49%
330 flights · avg delay 37 min
- 6 to 9 PM75%
185 flights · avg delay 20 min
- After 9 PM77%
127 flights · avg delay 21 min
Best day: Saturday (87%). Worst: Monday (81%).
Smarter routing
Nearby airports that run more on time
BUR → DEN 82% chance on time
Hollywood Burbank/Bob Hope Airport to Denver International Airport · 2,254 flights a year · 44 mi from your airports · yours: 78%
SNA → DEN 81% chance on time
John Wayne Orange County International Airport to Denver International Airport · 3,708 flights a year · 30 mi from your airports · yours: 78%
LAX → DEN 81% chance on time
Los Angeles International Airport to Denver International Airport · 7,729 flights a year · 47 mi from your airports · yours: 78%
LGB → DEN 81% chance on time
Long Beach International Airport to Denver International Airport · 1,014 flights a year · 36 mi from your airports · yours: 78%
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 aircraft39%
- Air traffic control and airport volume38%
- Airline (crew, maintenance, boarding)20%
- Severe weather2%
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
ONT to DEN questions
- What time of day is best to fly ONT to DEN?
- Before 9 AM: 91% of flights arrived on time, against 49% for departures 3 to 6 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 ONT to DEN?
- United, with a season-adjusted 83% chance of operating and arriving on time over 867 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 ONT to DEN?
- July (74% on time); the best was October (88%), 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 ONT
- DEN to ONT (return)
- ONT to PHX 83%
- ONT to SEA 86%
- ONT to LAS 78%
- ONT to DFW 78%
- ONT to SMF 86%
- ONT to OAK 87%
- ONT to SJC 86%
- ONT to SFO 69%
- ONT to SLC 91%
- ONT to ATL 90%
- ONT to PDX 88%
- ONT to IAH 85%
Live status: FAA delays and ground stops