Sunday, October 11 · typical odds for a Sunday (too early for a weather forecast) · issued Mon 12:00 AM ET · 8 nonstops

Sun, Oct 11: DL 4070 at 08:25 is the safest bet, 14% chance of being 15+ min late; evening flights run 21–34%.

Safest bet that day DL 4070 SEA 08:25 → ONT 11:17 · 14% chance 15+ min late · usually 89% on time Riskiest AS 489 SEA 20:33 → ONT 23:11 · 34% chance 15+ min late · usually 71% on time

Every nonstop on Sun, Oct 11

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	14%	5%	0.7%	89%
AS 476 Alaska	SEA 07:30	ONT 10:08	15%	3%	0.9%	no record
DL 4031 Delta flown by SkyWest Flight history →	SEA 14:30	ONT 17:21	18%	6%	0.7%	88%
DL 3884 Delta flown by SkyWest Flight history →	SEA 19:59	ONT 22:52	21%	7%	0.8%	84%
F9 2276 Frontier Flight history →	SEA 11:54	ONT 14:45	25%	7%	0.9%	88%worse than usual
AS 592 Alaska Flight history →	SEA 15:26	ONT 18:07	30%	8%	0.9%	75%
AS 571 Alaska Flight history →	SEA 10:30	ONT 13:10	31%	5%	0.8%	52%
AS 489 Alaska Flight history →	SEA 20:33	ONT 23:11	34%	9%	1.0%	71%

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 Sun, Oct 11 (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