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2,504 nonstop flights · Aug 2025 – Jul 2026 · US DOT on-time records, all US airlines

No clear winner: airlines and hours on this route all land within a few points of 83% on time.

Best time to leave 6–7 pm 95% arrive on time from SEA
Best single flight AS 1364 SEA 08:33 → ONT 11:14 · 90% on time Avoid AS 489 SEA 20:33 → ONT 23:11 · 71% on time

Time of day × airport

Share of this route’s flights leaving within 15 minutes, by airport and scheduled departure hour, over Aug 2025 – Jul 2026. Blank: no flights then (or fewer than 40 in the year).

7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
SEA
91
91
84
77
88
76
68
89
75
82
91
86
80
73
% of this route’s flights leaving within 15 min (small number: flights in the Jun 6 – Jul 31, 2026 schedule): 85+75–8465–7455–64under 55
Ontario flights leaving SEA 8–9 pm: 1Close ×
AS 489 SEA 20:33 ONT 23:11 2h 38m 197 71% 0.5% 43 min

Airlines on this route

Arriving within 15 minutes. Regional flights count under the airline that sells them. Pick an airline to see its flights.
Delta (incl. SkyWest) 1,076 89% 0.4% 51 min
Frontier 169 84% 1.8% 70 min
Alaska 1,259 78% 1.5% 47 min

Flights, best and worst

Flights in the Jun 6 – Jul 31, 2026 schedule that ran 150+ times in the year. Times are local. Pick a flight for its history.
AS 1364 SEA 08:33 ONT 11:14 90%
DL 4070flown by SkyWest SEA 08:25 ONT 11:17 89%
DL 4031flown by SkyWest SEA 14:35 ONT 17:19 88%
AS 592 SEA 17:51 ONT 20:32 75%
AS 489 SEA 20:33 ONT 23:11 71%
All 11 flights on this route →

Nonstops by airline and airport

Arriving within 15 minutes, Aug 2025 – Jul 2026. Pick a row to see that airline’s flights on that airport pair.
Delta SEA ONT 2h 48m 89% 0.4% 1,076 Flying now
Frontier SEA ONT 2h 46m 84% 1.8% 169 Flying now
Alaska SEA ONT 2h 41m 78% 1.5% 1,259 Flying now
Flying on a particular day? Pick a date above and the same ranking uses our forecast odds for each flight that day: Tomorrow.

About this data: US DOT on-time records, Aug 2025 – Jul 2026, all US airlines; regional flights count under the airline that sells them. Schedules (which flights and connections exist, and their times) are as of Jun 6 – Jul 31, 2026; seasonal flights outside that window aren’t ranked. Rebuilt monthly. JSON