Route on-time record
ONT to SEA: most on-time flights and the best time to fly
Ontario (Ontario International Airport) to Seattle (Seattle–Tacoma International Airport). 2,577 nonstop flights in Jun 2025 to May 2026, 86% arrived within 15 minutes and 1.2% were cancelled. The most reliable flight number was SkyWest 3690 at 7:00 AM.
Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.
ONT → SEA
Ontario to Seattle: 2,577 nonstop flights a year
On time (12 months)
86%
Cancelled
1.2%
avg delay 10 min
Best time to leave
Before 9 AM
93% on time vs 65% 6 to 9 PM
Most reliable airline
SkyWest
91% chance on time
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 · SkyWest 3690 · sold as United Express, Delta Connection, American Eagle or Alaska
7:00 AM → 10:07 AM3h 07m nonstop
Local times, typical schedule. Last flown 2026-05-06.
96%
chance on time
- On time (history)
- 100%
- Cancelled
- 0.0%
- Avg arrival delay
- 0 min
- Arrived on time 100% of the time (24 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 93% on time; 6 to 9 PM: 65%).
- Short track record (24 flights), so its score leans on the airline's record at this hour.
Limited track record · 24 flights
Find 7:00 AM flight fares Opens this date on Aviasales#2 · SkyWest 3816 · sold as United Express, Delta Connection, American Eagle or Alaska
6:45 AM → 9:49 AM3h 04m nonstop
Local times, typical schedule. Last flown 2026-05-31.
95%
chance on time
- On time (history)
- 96%
- Cancelled
- 0.0%
- Avg arrival delay
- 3 min
- Arrived on time 96% of the time (25 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 93% on time; 6 to 9 PM: 65%).
- Short track record (25 flights), so its score leans on the airline's record at this hour.
Limited track record · 25 flights
Find 6:45 AM flight fares Opens this date on Aviasales#3 · SkyWest 4042 · sold as United Express, Delta Connection, American Eagle or Alaska
6:00 AM → 8:55 AM2h 55m nonstop
Local times, typical schedule. Last flown 2026-04-12.
94%
chance on time
- On time (history)
- 94%
- Cancelled
- 0.0%
- Avg arrival delay
- 7 min
- Arrived on time 94% of the time (314 flights, Jun 2025 to May 2026).
- Never cancelled in 316 scheduled flights.
- Leaves in this route's most on-time window (Before 9 AM: 93% on time; 6 to 9 PM: 65%).
Strong track record · 314 flights
Find 6:00 AM flight fares Opens this date on Aviasales#4 · SkyWest 4070 · sold as United Express, Delta Connection, American Eagle or Alaska
11:59 AM → 2:55 PM3h 03m nonstop
Local times, typical schedule. Last flown 2026-05-31.
92%
chance on time
- On time (history)
- 92%
- Cancelled
- 0.0%
- Avg arrival delay
- 13 min
- Arrived on time 92% of the time (108 flights, Jun 2025 to May 2026).
- Never cancelled in 108 scheduled flights.
Moderate track record · 108 flights
Find 11:59 AM flight fares Opens this date on Aviasales#5 · SkyWest 4170 · sold as United Express, Delta Connection, American Eagle or Alaska
2:20 PM → 5:24 PM3h 04m nonstop
Local times, typical schedule. Last flown 2026-05-06.
92%
chance on time
- On time (history)
- 100%
- Cancelled
- 0.0%
- Avg arrival delay
- 0 min
- Arrived on time 100% of the time (24 flights, Jun 2025 to May 2026).
- Lands inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.
- Short track record (24 flights), so its score leans on the airline's record at this hour.
Limited track record · 24 flights
Find 2:20 PM flight fares Opens this date on Aviasales#6 · SkyWest 4031 · sold as United Express, Delta Connection, American Eagle or Alaska
5:53 PM → 8:50 PM3h 00m nonstop
Local times, typical schedule. Last flown 2026-05-31.
90%
chance on time
- On time (history)
- 90%
- Cancelled
- 0.3%
- Avg arrival delay
- 8 min
- Arrived on time 90% of the time (320 flights, Jun 2025 to May 2026).
- Lands inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.
Strong track record · 320 flights
Find 5:53 PM flight fares Opens this date on Aviasales#7 · Alaska 607
6:00 AM → 8:54 AM2h 54m nonstop
Local times, typical schedule. Last flown 2026-05-31.
90%
chance on time
- On time (history)
- 93%
- Cancelled
- 1.0%
- Avg arrival delay
- 5 min
- Arrived on time 93% of the time (200 flights, Jun 2025 to May 2026).
- Leaves in this route's most on-time window (Before 9 AM: 93% on time; 6 to 9 PM: 65%).
Strong track record · 200 flights
Find Alaska 607 fares Opens this date on Aviasales#8 · SkyWest 3840 · sold as United Express, Delta Connection, American Eagle or Alaska
1:35 PM → 4:35 PM3h 00m nonstop
Local times, typical schedule. Last flown 2026-05-31.
88%
chance on time
- On time (history)
- 88%
- Cancelled
- 0.0%
- Avg arrival delay
- 4 min
- Arrived on time 88% of the time (25 flights, Jun 2025 to May 2026).
- Lands inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.
- Short track record (25 flights), so its score leans on the airline's record at this hour.
Limited track record · 25 flights
Find 1:35 PM flight fares Opens this date on Aviasales#9 · Alaska 654
10:33 AM → 1:23 PM2h 50m nonstop
Local times, typical schedule. Last flown 2026-05-31.
86%
chance on time
- On time (history)
- 91%
- Cancelled
- 3.7%
- Avg arrival delay
- 6 min
- Arrived on time 91% of the time (210 flights, Jun 2025 to May 2026).
- Cancelled 3.7% of the time (8 of 218).
Strong track record · 210 flights
Find Alaska 654 fares Opens this date on Aviasales#10 · Alaska 729
3:26 PM → 6:17 PM2h 51m nonstop
Local times, typical schedule. Last flown 2026-05-12.
86%
chance on time
- On time (history)
- 95%
- Cancelled
- 0.0%
- Avg arrival delay
- 3 min
- Arrived on time 95% of the time (21 flights, Jun 2025 to May 2026).
- Lands inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.
- Short track record (21 flights), so its score leans on the airline's record at this hour.
Limited track record · 21 flights
Find Alaska 729 fares Opens this date on Aviasales
Airlines on this route
Season-adjusted chance of operating and arriving on time.
- SkyWest Airlines (sold as United Express, Delta Connection, American Eagle or Alaska)91%
1,113 flights · 92% on time as flown · 0.4% cancel
- Frontier Airlines85%
171 flights · 84% on time as flown · 0.6% cancel
- Alaska Airlines80%
1,264 flights · 82% on time as flown · 2.1% cancel
On time by departure time
All airlines, scheduled local departure, Jun 2025 to May 2026.
- Before 9 AM93%
744 flights · avg delay 6 min
- 9 AM to noon91%
575 flights · avg delay 7 min
- Noon to 3 PM79%
328 flights · avg delay 13 min
- 3 to 6 PM87%
659 flights · avg delay 10 min
- 6 to 9 PM65%
271 flights · avg delay 23 min
Best day: Saturday (88%). Worst: Friday (84%).
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
- Airline (crew, maintenance, boarding)41%
- Late-arriving aircraft37%
- Air traffic control and airport volume16%
- Severe weather5%
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 SEA questions
- What time of day is best to fly ONT to SEA?
- Before 9 AM: 93% of flights arrived on time, against 65% for departures 6 to 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 ONT to SEA?
- SkyWest, with a season-adjusted 91% chance of operating and arriving on time over 1,113 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 SEA?
- July (83% on time); the best was April (92%), 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
- SEA to ONT (return)
- ONT to PHX 83%
- ONT to DEN 79%
- 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