Friday, October 9 · typical odds for a Friday (too early for a weather forecast) · issued Sun 4:00 PM ET · 9 nonstops

Fri, Oct 9: DL 4070 at 08:25 is the safest bet, 12% chance of being 15+ min late; evening flights run 21–33%.

Safest bet that day DL 4070 SEA 08:25 → ONT 11:17 · 12% chance 15+ min late · usually 89% on time Riskiest AS 592 SEA 17:51 → ONT 20:32 · 33% chance 15+ min late · usually 75% on time

Every nonstop on Fri, Oct 9

12-month record →

Ranked by the chance of arriving 15+ minutes late (typical odds: the weather this date has had in past years), with each flight’s on-time record over Aug 2025 – Jul 2026 beside it. Times are local. Pick a flight for its forecast. Click a column to sort.


DL 4070 Delta flown by SkyWest Flight history →	SEA 08:25	ONT 11:17	12%	4%	0.6%	89%
DL 4031 Delta flown by SkyWest Flight history →	SEA 14:30	ONT 17:21	16%	5%	0.6%	88%
AS 1364 Alaska Flight history →	SEA 08:33	ONT 11:14	17%	3%	0.8%	90%
DL 3884 Delta flown by SkyWest Flight history →	SEA 19:59	ONT 22:52	21%	6%	0.7%	84%
F9 2276 Frontier Flight history →	SEA 11:54	ONT 14:45	24%	6%	0.8%	88%worse than usual
AS 565 Alaska Flight history →	SEA 10:25	ONT 13:09	27%	5%	0.8%	76%
AS 489 Alaska Flight history →	SEA 20:33	ONT 23:11	32%	8%	0.8%	71%
AS 571 Alaska Flight history →	SEA 13:50	ONT 16:30	33%	6%	0.7%	52%
AS 592 Alaska Flight history →	SEA 17:51	ONT 20:32	33%	9%	0.8%	75%

How these are worked out. Each flight’s odds are our forecast for that day (typical odds until the weather forecast covers it); flights of airlines we don’t forecast yet use their 12-month record and are marked. Makes the connection: the first flight’s 12-month lateness curve, scaled so its chance of arriving 15+ min late matches the day’s forecast, at the layover minus the 45-minute minimum (90 on separate tickets). Arrives on time: first flight not cancelled × connection made × second flight not cancelled × second flight within 15 minutes, each from the day’s forecast.

About this data: forecast odds from our model for Fri, Oct 9 (newest published update); 12-month records from US DOT on-time data, Aug 2025 – Jul 2026, all US airlines; regional flights count under the airline that sells them. JSON