Today: DL 4131 at 20:25 is the safest bet, 32% chance of being 15+ min late; the others run 42–56%.

Safest bet today DL 4131 SEA 20:25 → SMF 22:31 · 32% chance 15+ min late · usually 91% on time Riskiest WN 1769 SEA 20:00 → SMF 22:00 · 56% chance 15+ min late

Against a calm day 44% average chance a nonstop arrives 15+ min late; 34% 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. 16 flights that already left today are not shown.


DL 4131 Delta flown by SkyWest Flight history →	SEA 20:25	SMF 22:31	32%	9%	0.4%	91%worse than usual
AS 1427 Alaska Flight history →	SEA 20:55	SMF 22:48	42%	8%	0.3%	73%worse than usual
AS 722 Alaska	SEA 21:56	SMF 23:50	44%	7%	0.3%	no record
AS 681 Alaska Flight history →	SEA 20:19	SMF 21:39	46%	9%	0.3%	84%worse than usual
WN 1769 Southwest	SEA 20:00	SMF 22:00	56%	16%	0.2%	no record

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