Today looks rough: weather pushes the average chance of arriving 15+ min late to 52%, against 32% on a calm day. Safest: DL 3884 at 19:59, 40%.

Safest bet today DL 3884 SEA 19:59 → ONT 22:52 · 40% chance 15+ min late · usually 84% on time Riskiest AS 592 SEA 15:26 → ONT 18:07 · 64% chance 15+ min late · usually 75% on time

Weather 52% average chance a nonstop arrives 15+ min late; 32% for the same flights on a calm-weather day

Every nonstop today

12-month record →

Ranked by the chance of arriving 15+ minutes late, 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. 6 flights that already left today are not shown.


DL 3884 Delta flown by SkyWest Flight history →	SEA 19:59	ONT 22:52	40%	10%	0.6%	84%worse than usual
DL 4031 Delta flown by SkyWest Flight history →	SEA 14:30	ONT 17:21	40%	11%	0.5%	88%worse than usual
AS 489 Alaska Flight history →	SEA 20:33	ONT 23:11	62%	19%	0.9%	71%worse than usual
AS 592 Alaska Flight history →	SEA 15:26	ONT 18:07	64%	19%	0.7%	75%worse than usual

How these are worked out. Each flight’s odds are our forecast for that day; 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 4 (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