Route on-time record

SEA to ONT: most on-time flights and the best time to fly

Seattle (Seattle–Tacoma International Airport) to Ontario (Ontario International Airport). 2,577 nonstop flights in Jun 2025 to May 2026, 82% arrived within 15 minutes and 1.2% were cancelled. The most reliable flight number was SkyWest 4170 at 10:54 AM.

Flying on a specific date? We’ll adjust for the month, the weekday and the forecast.

SEA → ONT

Seattle to Ontario: 2,577 nonstop flights a year

On time (12 months)

82%

Cancelled

1.2%

avg delay 10 min

Best time to leave

Before 9 AM

90% on time vs 67% after 9 PM

Most reliable airline

SkyWest

89% chance on time

Check SEA to ONT fares

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 4170 · sold as United Express, Delta Connection, American Eagle or Alaska
10:54 AM → 1:39 PM2h 45m nonstop
Local times, typical schedule. Last flown 2026-05-06.
93%
chance on time
On time (history)
100%
Cancelled
0.0%
Avg arrival delay
1 min
- Arrived on time 100% of the time (24 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Short track record (24 flights), so its score leans on the airline's record at this hour.
Limited track record · 24 flights
Find 10:54 AM flight fares Opens this date on Aviasales
#2 · SkyWest 3840 · sold as United Express, Delta Connection, American Eagle or Alaska
9:45 AM → 12:35 PM2h 50m nonstop
Local times, typical schedule. Last flown 2026-05-31.
92%
chance on time
On time (history)
96%
Cancelled
0.0%
Avg arrival delay
1 min
- Arrived on time 96% of the time (25 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Short track record (25 flights), so its score leans on the airline's record at this hour.
Limited track record · 25 flights
Find 9:45 AM flight fares Opens this date on Aviasales
#3 · SkyWest 4031 · sold as United Express, Delta Connection, American Eagle or Alaska
2:30 PM → 5:13 PM2h 43m nonstop
Local times, typical schedule. Last flown 2026-05-31.
90%
chance on time
On time (history)
90%
Cancelled
0.3%
Avg arrival delay
5 min
- Arrived on time 90% of the time (346 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Strong track record · 346 flights
Find 2:30 PM flight fares Opens this date on Aviasales
#4 · SkyWest 3884 · sold as United Express, Delta Connection, American Eagle or Alaska
7:50 PM → 10:34 PM2h 44m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as SkyWest 3709, 4027; its record covers all of them.
88%
chance on time
On time (history)
88%
Cancelled
0.3%
Avg arrival delay
7 min
- Arrived on time 88% of the time (358 flights, Jun 2025 to May 2026).
- Departs inside SEA's trouble window: 54% of its 68 ground stops and delay programs started between 4 PM and 10 PM.
Strong track record · 358 flights
Find 7:50 PM flight fares Opens this date on Aviasales
#5 · SkyWest 4070 · sold as United Express, Delta Connection, American Eagle or Alaska
8:25 AM → 11:18 AM2h 48m nonstop
Local times, typical schedule. Last flown 2026-05-31.
86%
chance on time
On time (history)
85%
Cancelled
0.0%
Avg arrival delay
13 min
- Arrived on time 85% of the time (108 flights, Jun 2025 to May 2026).
- Never cancelled in 108 scheduled flights.
- Leaves in this route's most on-time window (Before 9 AM: 90% on time; After 9 PM: 67%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Moderate track record · 108 flights
Find 8:25 AM flight fares Opens this date on Aviasales
#6 · Alaska 1364
7:00 AM → 9:39 AM2h 39m nonstop
Local times, typical schedule. Last flown 2026-05-31.
85%
chance on time
On time (history)
89%
Cancelled
4.0%
Avg arrival delay
6 min
- Arrived on time 89% of the time (194 flights, Jun 2025 to May 2026).
- Cancelled 4.0% of the time (8 of 202).
- Leaves in this route's most on-time window (Before 9 AM: 90% on time; After 9 PM: 67%).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Moderate track record · 194 flights
Find Alaska 1364 fares Opens this date on Aviasales
#7 · Frontier 2276
11:51 AM → 2:35 PM2h 44m nonstop
Local times, typical schedule. Last flown 2026-05-31.
84%
chance on time
On time (history)
94%
Cancelled
0.0%
Avg arrival delay
3 min
- Arrived on time 94% of the time (16 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Short track record (16 flights), so its score leans on the airline's record at this hour.
Limited track record · 16 flights
Find Frontier 2276 fares Opens this date on Aviasales
#8 · Alaska 728
11:38 AM → 2:32 PM2h 54m nonstop
Local times, typical schedule. Last flown 2026-05-12.
82%
chance on time
On time (history)
95%
Cancelled
0.0%
Avg arrival delay
5 min
- Arrived on time 95% of the time (21 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
- Short track record (21 flights), so its score leans on the airline's record at this hour.
Limited track record · 21 flights
Find Alaska 728 fares Opens this date on Aviasales
#9 · Alaska 625
12:30 PM → 3:09 PM2h 39m nonstop
Local times, typical schedule. Last flown 2026-05-31. Same departure also flew as Alaska 664; its record covers all of them.
74%
chance on time
On time (history)
77%
Cancelled
1.4%
Avg arrival delay
12 min
- Arrived on time 77% of the time (144 flights, Jun 2025 to May 2026).
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Moderate track record · 144 flights
Find Alaska 625 fares Opens this date on Aviasales
#10 · Alaska 592
3:37 PM → 6:13 PM2h 36m nonstop
Local times, typical schedule. Last flown 2026-05-31.
73%
chance on time
On time (history)
77%
Cancelled
0.0%
Avg arrival delay
11 min
- Arrived on time 77% of the time (172 flights, Jun 2025 to May 2026).
- Never cancelled in 172 scheduled flights.
- Departs outside SEA's trouble window (4 PM to 10 PM, when 54% of its 68 ground stops and delay programs started).
Moderate track record · 172 flights
Find Alaska 592 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)89%
1,112 flights · 90% on time as flown · 0.5% cancel
Frontier Airlines78%
171 flights · 76% on time as flown · 1.2% cancel
Alaska Airlines75%
1,265 flights · 76% on time as flown · 1.8% cancel

On time by departure time

All airlines, scheduled local departure, Jun 2025 to May 2026.

Before 9 AM90%
617 flights · avg delay 7 min
9 AM to noon84%
349 flights · avg delay 8 min
Noon to 3 PM81%
634 flights · avg delay 11 min
3 to 6 PM68%
250 flights · avg delay 17 min
6 to 9 PM86%
495 flights · avg delay 8 min
After 9 PM67%
232 flights · avg delay 18 min

Best day: Tuesday (87%). Worst: Sunday (79%).

Smarter routing

Nearby airports that run more on time

SEA → SNA 84% chance on time
Seattle–Tacoma International Airport to John Wayne Orange County International Airport · 3,972 flights a year · 30 mi from your airports · yours: 81%
Rank flights Fares

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)48%
Late-arriving aircraft32%
Air traffic control and airport volume13%
Severe weather7%

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

SEA to ONT questions

What time of day is best to fly SEA to ONT?: Before 9 AM: 90% of flights arrived on time, against 67% 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 SEA to ONT?: SkyWest, with a season-adjusted 89% chance of operating and arriving on time over 1,112 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 SEA to ONT?: August (77% on time); the best was October (87%), 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.

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